Boyfriend on Facebook

Me and my boyfriend were together 3 years before breaking up. He broke up with me for 6 months last December and in that time he was seeing other girls. We got back together about 2 months ago and so far everything has been great. Im also pregnant with our baby boy. This has only started bugging me recently, he still acts single on Facebook. He still posts quotes that a single person would say, posts pictures of himself that loads of girls like, he doesn't give any indication what so ever that he's with me. I don't care that he has Facebook and posts photos of himself. I know that girls liking his posts doesn't mean he's talking to them. but I'm a little insecure and it would make me feel a lot better if we could make it 'Facebook official'. Since being back with him I don't bother with my Facebook, the only posts I make are about the baby. I recently found out he secretly changed my password and has had it all this time. I don't have his. I leave my phone out every time he comes round and he can go on it whenever he likes. Just normal things that a loyal girlfriend does. When he comes his phone is either dead or he just doesn't get it out at all. I asked him the other day if he's still talking to other girls and he said no. I asked him if he would be okay with me posting pictures of myself on Facebook also and he said no. If he made posts with or about me too it would be different. But because he doesnt, when he posts pictures of himself I can't help but think it's obviously for attention of other girls. He sees all of the guys who try to message me and I ignore them. I even put a status asking for guys to stop messaging me as I'm in a relationship and it's getting annoying. That was off my own back I was generally getting annoyed with all of the messages. How do I know he's not getting messages of girls and replying? He knows I don't reply because I let him on my phone whenever he likes and he's had my password which I didn't even know until yesterday. I probably sound so stupid and paranoid but hopefully someone gets me. I never seen anyone else during the breakup, he finished with me and i wanted him back. Him seeing other girls is what is making me a little insecure now. However i wouldnt feel this way if he would just let people know that hes with me now. I really feel like hes keeping me a secret just so he can see other girls. I now want to ask him if we can change our relationship statuses on Facebook for everyone to see so i can see his reaction. How do I ask him this in the best way? If he says no, should I leave?