The first time John let Sherlock touch him was a mistake.
Their cute fast hidden little kisses soon turned into full on snogging sessions, and those soon turned into John up against the wall, or a table, or Sherlock's bed.
But this time John let Sherlock continue.

Once the kissing soon got passionate, Sherlock pushed and began moving both of their bodies towards his bedroom. In a drunken slur of emotions, they both started to remove each others clothes, John not even realising the full of what he was doing, and what he would be doing in the next few minutes.
John lingering in each and every kiss began to feel addicted to Sherlock's full on kissing, and once he removed his lips for only a minute John began to moan in the absence.
While John was fusing over the leave of Sherlock's lips, Sherlock him self was scavenging his bedside cabnite for what was contained in a small plastic bottle.
John still sick from the leave of his lips noticed the bottle,
"What is it?"
Sherlock snickered as he placed his lips on John's once more.
"What do you think it is?"
Sherlock's hand dropped from John's shoulders to his lower stomach, with each and ever touch John got even drunker with lust. Well a where that his partner was getting quiet aroused from just touch and kissing, Sherlock's hands danced around John's bower hem.
A moan escaped John's lips.
A signal to continue.

John found that a person grabbing his ass had never felt better.
After Sherlock had removed both his and John's underwear, he shifted and started to move John's ass closer to him.
Sherlock reached or the bottle and sprayed some of it's continence onto his hands. He brushed on of his fingers up against John's bottom.
"Ahh-" John groaned, the cold fingers now surprising him. He looked Sherlock in the eyes, and Sherlock began to push in.
One finger is actually quiet hard the first time,
your not expecting it, so your body tries to repel it, only turning your partner on by how tight you are. And with the sudden shock of realising that someone is actually inside you, you even tend to get a bit uncomfortable and hurt.
Although it is reasonable to presume that the first time would hurt, and it does.

John squirms as Sherlock moves farther in, he gasps as Sherlock removes his finger. Almost needing that burning sensation again. Yet as a surprise, Sherlock thrusts two fingers in.
Two fingers is easier, since you're already lubricated inside and slightly stretched out.
This round John finds it easier to enjoy. He's moaning and very hard.
After awhile, three fingers.
Both of them are panting, and John's now moaning constantly, and begging for more. With each push he feels more pleasure, and is now thrusting his hips into the action.
As Sherlock removes his fingers, John can't help but feel empty, he calms down his breathing and is now semi normal.
Then Sherlock actually thrusts in.
He moans so loud he's scared he'll wake London up.
With each thrust John's body burns more and more up.
With each thrust John can feel his orgasm coming up.

And then,
he feels something amazing.
Sherlock hits his prostate and slides past it, sending Johns body into a whirlwind. He's body's on fire, and he's visions gone cloudy. There's so many fireworks he doesn't know where to look.
And suddenly there's only white.

He can feel Sherlock come too, which is an even odder feeling since it's inside of him, yet it sends him right up the charts again.

John can't breath.
Sherlock exits him and lays on the bed beside him.
Both panting hard.
"Well, that was quiet an experience," Sherlock muttered, his eye lashes fluttering in beads of sweat.
John punched him, "Shut up idiot and kiss me."

(AN: this is my first try at a sex scene so don't kill me.)