Confused.

I'm very confused & frustrated with myself. I have been dating this guy for almost two months & the last two weeks we have been separated just because of the simple fact we're so different, we fight all the time, there's drugs involved mind you I'm not the one on them! It's just very complicated. Lately things have been hard, I'll go stay with him and all we do is fight & have sex. I had my Nan pass away & he couldn't even be there for me the way he should have been, instead he was out doing drugs with his friends, I have caught him out that many times lying to me about what his doing & if his doing drugs & all he does is get very angry at me.  We have good fays but mostly bad. When we fight its bad, he makes me feel very useless & I contemplate myself quite a lot, I'm also 19.  I cannot help but go back, I do have feelings for him, but I think it's just the simple fact I'm lonely? SOMEONE GIVE ME SOME ADVICE PLEASE!