Troubled Relationship

I'm in a real jam and need help. My boyfriend and I have been official for just over 4 months, I've been seeing him since January though. WARNING THIS IS A LONG READ but I need help... We are on the same team at our job (we've got 5 people). We met at work and started dating. before we were official, he told me how he never hooked up with anyone (we started at FWB) and has never fucked with anyone from work. After clicking on a podcast type thing off of one of my Facebook, it was my friend/coworker with her friend (used to work at our job and now does again). He said he didn't want to watch it and told me that he had fucked my friends friend before we started dating because he wanted to convince himself that he didn't have feelings for me (he also fucked her once before I met him). The fact that he had relations with another girl didnt bother me, it was the fact that he lied and said he wasn't fucking with anyone else (I was honest and told him that I was also seeing someone else at the time, another FWB). On another occasion, I found a bag that previously had coke in it. I was pissed because I thought it was my roommates, but he said it was his roommates (our roommates were also seeing each other). I was still pissed but not as bad because I don't care for my roommates boyfriend. Then my roommates boyfriend told me months later that yes, he has done coke but that the bag I found was actually my boyfriend's bag. I asked my boyfriend for two weeks straight if he's done coke and he kept saying no. I finally told him that i was going to ask him a question and he better be honest with me. He finally admitted it to me. He's been planning to go to this festival in another state for a couple months now and he'll be gone for about a week. I don't trust him to go and he knows that, but he's still going. I feel so unimportant and I know he won't do anything, but the back of my mind questions it, constantly! He also does molly, which I knew. but now I don't want him to do it. He says he wont, but how can I trust him?