Is he making me the side guy?

I recently got out of a rocky relationship a few weeks ago after my boyfriend of a year broke up with me, and it was pretty bitter. During our relationship, he constantly cheated on me, talked to other guys, and even stayed in contact with his exes. We stopped having a lot of contact in the past couple weeks as I found out he started to talking to another guy within a few days after we broke up. He admitted that he was talking to another guy but told me we shouldn't be friends and that I need to leave him alone- he was very rude and standoffish towards me. I left him alone and went about my business and I started taking steps to get over him.

Last week, he started being nice and doing favors towards me. I told him I wasn't comfortable with him doing things for me and he said he wanted to be friends with me. Him and I had a meeting to attend together for school the other day, I was not able to make it and I told him I would not be attending the meeting and he got very upset about it. He said it was important for me to be there and that he would really like it if I came. During the meeting, I would catch him looking at me for a couple seconds. I don't want to say that I am jumping to conclusions about him having feelings for me again, but how can you go from one extreme to the other? He did this exact same thing in our relationship with his previous ex boyfriend. I think he has a serious problem with being faithful. Would you be suspicious? Should I stop contacting him? I don't want to be some side guy and if he is crossing boundaries, I don't want him doing that to his current boyfriend- even if I don't approve of their relationship, I don't approve of cheating either. Opinions? Advice? Thanks!