He has a girlfriend but still acts interested?

Alright so my crush has a so called "girlfriend". He never really brings her up and when he does it's only because his friends do and he is inclined to respond. Like today, his friend was making fun of him saying his girlfriend and him haven't talked for over a week. Someone asked him why and he said he hasn't texted her since she never responds to him.
The unfathomed day I find out he was with this girl, he didn't tell me himself which was odd because we talk about everything. I found out because their friends posted a pic of him and her hugging. When I asked him about it, he denied her as well saying they weren't "official." A week later they broke up b/c she didn't think he cared and was mad because of the pictures other people posted? but then three weeks later I find out they're still together. But throughout this whole ordeal, I am genuinely convinced that he likes me as well. Why? Well for starters he follows me around like a lost puppy and wants to talk to me every waking moment as well as talking to me about everything (that's not about his girlfriend) . He also texts me quite frequently with memes, and the occasional conversation. He gets mad when I ignore him (but does it to me too anyways). Always trying to find out my business. He's also very touchy as well. I'm standoffish. I don't exactly initiate anything, frequently ignore him, and leave him on read when he texts me. Not to mention, I did tell him I like someone else.
Honestly, up until today I thought he was single again. He has yet to ever mention her to me besides when I asked him about their relationship. From what I've been told, it was common fact she liked him and his friends "forced" him to ask her out. She's also very attractive as well.
I do feel bad from the way his relationship is going for him. Considering it is his first one. Even though, I am mean to him right now I wouldn't be at all that way if I had him.
What should I do? fess up? tell him what I f
He has a girlfriend but still acts interested?
2 Opinion