Guilted into seeing someone

A few weeks ago I went to my friends birthday party. Her boyfriend brought a friend and I didn't know who he was but I thought he was cute. So I told them and they tried setting us up. We ended up making out and I was trying to have sex but he said he would rather take me out first. He asked me out for dinner that day but I was hungover so I said no... The next day he comes to my workplace while I'm trying to close and I'm putting in my 2 weeks notice. He's just standing there for like a solid 30 minutes which left me feeling kinda weird... Well we went to his car to talk and he started talking about his ex and how they both ducked each other over for about an hour... So I was just kinda like okay then I found out they had literally broken up that week and he told me that he had texted her the day of the party trying to talk to her again but that she wasn't responding. Also told me that he had bought plane tickets for her to come in that Friday (3 days from the day he saw me) and that he needed to cancel them. This plus the fact that he still had pictures of her on his Instagram led me to believe that he wasn't over her.. I just feel like he'd be really clingy and I can't deal with that. He just deleted his exes pictures yesterday. And yesterday I sent a snapchat to my friend and she got kinda shitty about me not going out with him. I don't know how to explain that I'm just not into him and I feel like it's gonna make hanging out with this friend group awkward.