Possible interest?

Hi! So, I've known this guy for like 5 years. We've been pretty close friends since college, always sharing conversations about interests, school and such. I always thought of him as pretty cool, but often very reserved, yet seriously outgoing and not shy to talk to random strangers. I thought of him as a possible interest for dating, but I had a boyfriend by then for two years. Recently we broke up (like the beginning of this month) and I've been trying to get over my ex (in all honesty, it wasn't even working well near the end of the first year). But now the 5-year guy happened to land the same job and position as me, so we're working as co-workers. It would have been fine and all, but he confessed his interest in me last year while I was on my break from my ex. We're still cool, but idk I think he's still interested, yet he's so damn reserved. I know it's bad to date co-workers, and while we have alot in common, and he does care, help me out, and cheers me up, I'm having constant conflicts of being interested and saying he's just a friend. I think it's part of the process of getting over my ex. But still, I feel bad because, now that I think about it, sometimes I ignore him or act cold/distant when he wants to help me. I'm such a jerk...am I slightly falling for him or am I trying to find an excuse to be with someone after my break-up? I do care for him, but I'm scared that despite our commonality, what if we do try to get together and things don't work well? Should I try? And how long should I wait, because I'm in no mood to really try things at the moment... I'm really sorry if there are any contradictions! I'm so confused and trying to get over things at this time that I don't really know anymore. Any feedback will help! Thank you guys for your help!