Why does my bf act like this and what should I do?

I love my bf and he’s amazing. Always has been good to me. I just noticed that whenever I’m on my phone (to just check it), he looks at me then reacts in a way of bringing up random stuff and making noises sometimes. Idk if that’s something. I asked him if he’s okay and if it bothers him and he said No and that it doesn’t bother him at all and that I can do whatever I want.

The thing is though, he’d keep doing it. I asked if he’s okay and he’d be like “Yeah! I’m fine!”

He’d look at me and then sigh loudly bringing up his parents

It just seemed like a fake reaction…

I usually comfort him about it. I just had this feeling that he just brought it up to grab my attention.

I don’t know what to do. He already said nothing is wrong. This still bothers me though.