what should I do?!

My boyfriend of 7months has started a new work place and he has created new friends that sleep around etc. He has started texting girls because of this one friend Let's call him Ben. Ben has Told him to text numerous girls and he does? He always keeps his phone too himself and will never tell me anything, he would hide his phone so I couldn't see who he was texting or anything! 
A few weeks later, he keeps making petty little arguments about me being miserable ( when I'm really not) I had a bad patch a week before this where I cried all the time but the following week I was fine, back to My normal happy self. He calls me a miserable bast*rd and a miserable c*nt and that I make his life awful and that he's sick of me. HE WAS EVEN ON HIS PHONE DURING SEX! COMPLETELY IGNORING ME 
What do I do?!? Please help and suggest some things please