Anxiety Attacks

Ugh! I've always been a calm go with the flo kinda gal. I'm 22w2d pregnant with my first baby and I have anxiety attacks all the time!! I don't have a bump, can still lay on my stomach. I freak out! I feel my little girl move, never have any bad dr visits. I'm a perfectly healthy 18 yr old girl, with a healthy pregnancy. Why do I still freak out???