How do I know if my gums are healthy?

My teeth are beautiful. But I think my gums are getting loose. When I floss, there is so much space now. Can your gums shrink away from your teeth? Can I plump them up? (They look fine, but I feel a difference).

I know I am bad, but I really do not want to see a dentist. Just thinking about it, my heart is beating faster...

I appreciate your advice.