Why is my FWB and ex so confusing, or is it just me?

Okay, so I’ve been seeing with guy D for almost half a year now, and we’re just FWB, that doesn’t bother me. But lately he’s been saying and doing a lot of things that I don’t really know how to deal with. He’s been joking about kids for one thing. Asking me if I thought it was about time he got some (he’s 31) and I said that it was up to him and that he just needed to find a nice girl to have them with, and then he said that I could just stop eating my pills. He says it’s just a joke, but yeah. Also, on a dating site, whenever someone my age contacts him he says that he thinks they’re too young, honestly I feel a little insulted when he says that – I’m old enough to f you c k but not anything else? Also last weekend he was here, he made a great deal out of being really romantic, filling my room with candles and making love to me. Usually we’re a bit more rough around the edges if you know what I mean. And every time I’m with another guy (We’re okay with that as long as we protect ourselves so we won’t be passing on nasty things), he get really sad and keeps asking what’s wrong with him as I don’t want him, but still denies that he has feelings for me. So I’m a little confused, just what’s up with him?

And then there’s my ex, who was also in my last question on this site, he’s told me that he’s not so sure any more that he made the right choice back then to break up with me and he gets jealous every time I mention D or any other guy I like a little, even though he knows how I still feel about him (he was my first love, don’t think I’ll ever stop feeling something). We’ve had sex recently, and he’s been really gently and didn’t “force” me into anything and it felt so right, but I don’t really know anymore. I don’t regret what we did, but I don’t want him to just use me, that’d hurt too much. Part of me wants him back, and part of me is screaming at me to get the hell out.

So, people… what do you think?