He has not given me reason to assume he is seeing others (or that he got back with his ex). He is increasingly becoming closer to his male friends (has a lot of female friends too, but mostly males recently).
The thing is that he's been good overall and probably a lot better than the guys I've dated these past two years. Still, something about his demonstrable level of interest is not making me feel secure or happy at the moment. Perhaps I expect too much too soon (it's been less than 2 months), which is something I have been accused of before, but I find that INFJ intuition can be very strong in these instances.
Again, my experience with an ENFP talking here. But I do think you might be expecting too much too soon. I get the impression that NFP's really don't like the idea of anything that suggests committing or taking things too seriously, but it doesn't mean they don't really really like you or that it won't eventually lead there. Their love language is very present moment oriented but very passionate when in that moment. I've assumed otherwise and ended up just hurting/offending/scaring the ENFP I was into for a while. Take it easy, don't over analyze, and learn to appreciate the present moment with them. (perhaps this is best advice for the starting stage of all flings/relationships).