I live with my boyfriend and whenever he's not around my heart kinda beats weirdly and I feel super scared. Just wanted to know if that's okay?

I'm constantly waiting for him to come back and be with me 

I'm also afraid to tell him about this for two reasons:
1. I don't want to push him away - because knowing him he'll say that I need to learn how to live alone and he'll just leave
2. I'm scared he won't believe me about the scary heartbeat and the irrational fear because when he's around I feel perfectly normal and fine

Any comments would be super helpful:)