Well here is at least the start of the wedding... in case it's confusing it DOES switch between their POVs. I know I haven't done this for the rest of the fic but I wanted to show both of their thoughts and perspectives for this part. I hope you enjoy!
I sat in the dressing room alone, still trying to choose a tie. The wedding, my wedding, was only an hour away and I still couldn't make up my mind. It was more than jitters, I was confused. Was this the tie I really wanted? I knew deep down that I would be happier if I wore the other tie. It was laying on the chair and I thought about how great I'd look with it. How much I loved that tie. It was the tie that Robin bought me when we were dating, and it always reminded me of her. I couldn't wear it of course, not to my wedding to Summer, who I loved. I did love her too. And the last thing I needed out there was to be wearing a tie that still sort of smelled like Robin. That would just complicate things, which was what I was trying my best to avoid.
I laughed a little at that last thought, because I was doing a terrible job of it.
So, I wore the other tie, it didn't feel right, but I had made my choice and there was no going back. I paced the room, trying desperately not to think about Robin. I was far too aware of the note she'd left for me which was still folded up in my shirt pocket. I'd kept it with me since the day I found it, re-read it more than I should have. I thought that maybe I shouldn't have it with me for the wedding, but I couldn't bring myself to leave it here, or anywhere. I resisted the urge to read it for what must have been the hundredth time.
…
I took in my surroundings; everything was so… so beautiful. So romantic, it made me want to cry. I felt my eyes beginning to water and used every ounce of willpower I had to stop the tears from rolling down my face. I couldn't believe I was here, after months upon months of dreading this moment, it was here, and it hurt. I hurt like nothing I have ever felt before. I thought the lead up had been painful, like millions of knives cutting deep scars into my heart, but this, my world shattered as I look up to the altar to see the man I loved. The man who used to love me, in his fine Italian suit, preparing himself for the same thing I was. For that moment when Summer would walk through those doors, in a beautiful white dress, smiling at the man she was about to marry, the same man that I loved. He would gaze into her eyes, and promise his love for her, that she would be the only women he loves. I couldn't take it anymore.
…
This was it. Everyone in the room was anticipating the same thing, their eyes glued on the entrance, where Summer would walk down the aisle in a beautiful dress. My eyes however were frantically scanning the room, looking for Robin. I spotted her near the front, sitting alone. She looked beautiful, her hair framed her face, falling in shiny chocolate-coloured curls. Her skin was so radiant she looked like an angel. Her dress was perfect, it clung to her in a way that was sexy, but not slutty, it somehow found a way to make her body even more magnificent, something I didn't believe to be possible. And even from this distance I could see her eyes, tearstained, and filled with the colour of the ocean itself. The same eyes I fell for.
The door opened and Summer emerged, looking quite stunning. I watched her walk towards me, still taking small glimpses here and there over at Robin. I couldn't resist. That's when I realized something, Summer was gorgeous. I was extremely lucky to have her, but even after hours of being perfected with makeup and hair stylists she was still not as beautiful as Robin was in my eyes. Robin wasn't perfect, but it was her imperfections that made her so incredible. I loved her for everything that she was, a mess at times, but the most amazing mess I'd ever layed eyes upon.
Summer arrived at the aisle, and I used every bit of willpower I had to tear my eyes away from Robin. In a way, I sort of blanked out, every sound around me was blurred together and felt distant. I thought about Robin and everything we'd been through together, how much she meant to me, the terrifying fact that I'd literally do anything for her. And then I looked back at her, I noticed her face. Robin was amazing at hiding her emotions, but not from me. Only a small glance at her face and I knew. Her face was incredible that way, she was never a touchy-feely-talk-about-your-emotions type, and her face said all the things she was too afraid to. Puffy cheeks, smudged mascara, slightly red nose... whether or not anyone else saw it, I could tell she'd been crying.
I can't believe how long it took me to realize how big a mistake I was making. I was simultaneously hurting Robin, the love of my life, and lying to everyone around me, all because I was so damn afraid of being with someone I loved. Love is scary, it means giving your heart to someone and with it the ability to tear it to shreds. You let someone fill your world and be your other half and if you lose them you become empty and incomplete. Love means taking a risk, but the truth is you don't have any say in the matter. I never chose to love Robin, and getting married won't make me stop loving her. Nothing will.
"Does anyone have any reasons why these two should not get married?"
A million reasons bounced through my head. What the fuck was I doing?
"Speak now, or forever hold your peace."
…
This was my last chance. I looked at Barney, trying my best to hold back millions of words, millions of reasons why they shouldn't get married. I'm a mess and I don't know how to deal with my emotions, all I know is that I love him. I could never admit it before but it's the most true thing that's ever gone through my head. And I loved him more than I believed possible. I just couldn't shake this feeling that we belonged together. I wanted to stand up and say that more than anything, but I loved him too much. I remembered what Ted said a long time ago, "Sometimes if you love someone you should want them to be happy, even if you end up getting left out." He was right, I wanted to be with Barney more than anything but I couldn't do this to him. I had my chance, and I blew it.
In my life I'd had a couple of moments that had truly lasted a lifetime, but this one, this silence lasted a million. I knew this was it, I tried to let go.
"I have a reason." It was Barney's voice that broke the silence.