overly jealous so?

me and my so have been dating for almost a year now we are having a baby in august. and were both jealous people I'll admit but, lately he's been out of control jealous for no reason or protective of me. last night we had a huge argument because I looked at a guy for ten seconds and I didn't realize I was looking. I told him after that if he continues I will leave. now today he got upset over me posting I'm in a "cuddly mood" publicly. is he really overreacting. I don't know how to handle this anymore, advice please if you've gone through a similar situation.