My bf is bored?

Ok. So this is going to be long.. fair warning! But I don't really have any girl friends or friends in general who will listen and take me seriously. My SO and I have been together 4 years on & off. (Mostly on) we are long distance, we also play video games together to keep things interesting and we video chat when I can get him to. Ok now you have a small background of us.

Recently, I've felt he's been more distant. He use to always text/call me. We use to talk for HOURS on end. But recently I can barley get a quick reply, he typically takes 20 mins to a hour to reply now and he mostly talks sexual bc he "can't find anything to talk about". Yesterday he tried to blame me when I got upset with him about always talking sexual, he said I needed to start thinking of conversation starters also. But !! Tonight has been the icing on my cake, I know quite a few of his friends via the video game & meeting them, I became friends with his best friend (we'll call him A) today was A's birthday, I knew the whole squad of guys was going out for A's birthday today and all, but when we started trying this afternoon I had assignments I had to finish and he was going to play video games before he had to leave, so I just told him we'd talk later, he ended up leaving without sending me a goodbye message, or calling and telling me he had left. (He wasn't going to text me while out for A's birthday & that's totally understandable) he was gone 6 hours, as soon as he got home (or he says he had just got home but A had been home a hour before him and he was suppose to be with A, since A dropped him off) either way, he was gone 6 hours, but we hadn't talked for (8-10 hours), so after all this time when he does text me, after 5 or so minutes of conversation, he gets all sexual on me, trying to dirty talk and all. I shut him down by saying I wasn't in the mood. He got majorly upset with me and made me feel bad for not being in the mood, we quickly talked it over and fixed our issue and I found us something to talk about. Sounds like a good ending right? Nope!! I found us something to talk about which he said was what I needed to do and it's been two hours and he hasn't texted me back! Or even bothered to say goodnight or anything. (It's nearly 6am for me, nearly 3am for him) I stayed up just to talk to him and it seems like he doesn't want to talk to me? what should I do? I really needed to vent and I just don't know what to do. I love him so so much and don't want to lose him but I feel so unappreciated! It's always sexual with us, or not talking at all! He is always stuck up his friends ass on the video game, and if I join them on it and becomes a asshole.. I need all the help I can get please!