A/N: Replaced from Sherlocks point of view.
Before John, Sherlock went over to Lestrade's all the time. At random hours of the day, no matter if Lestrade was home or not, he just went over.
It had started when Sherlock first tried to sober up. Lestrade had found him at one of his usual drug-dens and, after Sherlock had deduced everything about Lestrade's life, Lestrade had offered him a place to go to when he needed the drugs to much. To prove to himself, Mycroft and Lestrade, that he could go without, he took him up on the offer.
Lestrade's wife hadn't quite liked it, had made it obvious by pursing her lips and glaring at the both of them. But seeing Lestrade shrug whenever those eyes landed on him, Sherlock had been able to brush them off too. Eventually, the wife left and Sherlock still went over.
In the beginning, he went over almost solely in the evenings, when Sherlock had deduced the time that Lestrade and his wife usually got up to prepare for bed, and he slept on their couch. He would make sure to leave in the mornings, as to not antagonize the wife further and make Lestrade's life more difficult. But one day he slept longer than he had anticipated and Lestrade had made them breakfast. The kitchen was silent, Sherlock not daring to speak and the wife glaring at him as if she could glare him out of her kitchen. She couldn't, the only reason Sherlock would leave was if Lestrade would ask him to. He didn't, and he even made stupid jokes to try and cut the silence. Sherlock grinned at him in fondness and the wife rolled her eyes. Gradually over time, it started happening more often that he'd stay for breakfast.
After about 6 months, Sherlock had a really bad night and he went over earlier. Lestrade had been surprised but he had let him in, ushered him to the couch and sat next to Sherlock, as if sensing that all that Sherlock needed was company. Lestrade sat down next to him, and Sherlock heard the wife huff in annoyance when Lestrade just turned his attention to the television once more. She left for bed and Sherlock fully expected Lestrade to follow her. He didn't. He stayed for a bit longer, until it was the usual time that he'd go to bed and Sherlock grabbed his hand quickly in thanks when he got up. The smile on Lestrade's face made his heart skip a beat. This too became a regular occurrence.
It didn't happen often that Sherlock went over, at most once a week, mostly on the weekends when he knew Lestrade wouldn't have to get up in the morning to go to work. He still didn't want to inconvenience the kind man more than he needed too. After the wife left, Sherlock sensed a loneliness in Lestrade and he started going over more often, up to 3 or 4 times a week even. Sherlock was glad that he could help Lestrade for a change.
Lestrade gave Sherlock a key when the wife left. Sherlock narrowed his eyes at Lestrade, and realised it was an invitation to come over more often, he nodded in acceptance of the invitation and he started showing up for dinner after that. They'd work around each other in Lestrade's tiny kitchen to prepare the dinner and during the preparation the smells would often make Sherlock so hungry he'd actually eat any of it. The fact that he didn't eat often when he wasn't with Lestrade didn't help his hunger either.
Feeling that Lestrade wouldn't mind it when Sherlock went over when the older man wouldn't be home, he came over during the day also. He never really experimented in the other's house, but he did work on his laptop often, researching one thing or another for one of his cases. When he'd get stuck on something, he'd get up to eat a pudding, or make himself some coffee to distract his mind from the problem. In the summers when it was too cold in the morning without a coat, he'd often forget it when he'd leave again and it was warm enough to go without. Sherlock liked that he left traces of his presence in Lestrade's life, feeling welcome to for once, and it made him feel a bit less lonely when he wasn't over at the other's house.
Then John came along and he questioned Sherlock about relationships. Sherlock realised that what he had with Lestrade was a relationship. Not a sexual one, and it terrified Sherlock that he could see it happening over time that it did become one. He was fond off the other man and he knew that it wouldn't take much before he loved him, and frankly that terrified Sherlock even more. Everyone that he had ever cared about, had left him. Redbeard had to be put down when he had fallen off a cliff when the dog was 4 years old. His best friend Victor had moved away from the little town that Sherlock had lived in. Mycroft went away to college. His grandmother had died three years ago. Sherlock didn't want to have to grieve for losing someone he was in love with, knowing it would destroy him, so he tried to detach himself from the older man, going over less and less. He missed Lestrade when he didn't go over, but he knew it was necessary. As Mycroft had once told him, caring wasn't an advantage.
After a few months Sherlock realised that he'd never be able to stop caring about the other man if he still went over when he really needed him, so he stopped. He'd only see him on cases now, and he knew that would have to be enough. Sherlock lost weight though, not nearly eating enough, although John kept nagging him about it, but not in the mood for cooking when he couldn't cook with Lestrade.
Sherlock would frown whenever he saw Lestrade stretching out his back on crime scenes, and after a while he deduced that Lestrade had started sleeping at the couch in his office. He didn't comment on it though, knowing that if he would, Lestrade would either avoid his questions or start asking questions himself, and Sherlock wasn't nearly ready to face them. Lestrade avoided eye-contact though, so it wasn't that hard to keep himself from commenting on it.
Sherlock knew Lestrade thought he had been replaced by John. He wasn't, nobody would ever be able to replace Lestrade, and by God, he missed him.