I think he is cheating on me?

I have been with my boyfriend for almost 7 years now and I do love him so much we have had a very stressful relationship but this past year he has changed. I have to admit I did cheat on him before but I have changed for him I don't have no friends no more I suffer from depression and anxiety so I feel like that might be the reason I feel like this. I constantly catch him watching porn and video of girls shaking their ass he always puts me down saying I'm a slut fat slag and dog extra he says he only says it when he's angry and doesn't mean it but its always the same thingd. He only ever wants to have sex from behind I don't know if I'm going crazy or have I got something to generally worry about thanks guys