I think my partner is struggling

So I am 21 Weeks pregnant. Lately I noticed a change in my boyfriends mood and overall presence. One night he told me when I was sleeping he put my hand on my belly and felt our baby girl moving around for a while. But then the next day he was telling me how he is struggling with certain things. Things that are kind of random and not really that much even about our relationship. And how things are becoming more real and it’s left him really contemplating lots of things. We have a great relationship and never get in fights so it really threw me off and left me feeling kind of insecure all of the sudden. I’ve also noticed a lack of intimacy. He did tell me he finds it a little weird being intimate knowing she’s in there moving around and such. And he has been kind of less clingy. Did anyone else have this happen to their partner? I read online about how men can experience pre-post depression too from the changes and such and I just don’t know what’s the best way to go about helping him feel better. I am super sweet and reassuring everyday. I just feel really weird and I hate that he’s going through these changes..