One if my gums is almost hanging down on the left side of my tooth and I really don't know what that is. I'm scared it might get swollen.

You're correct.. ... it can quickly get worse. That's why you need to see a dentist ASAP to have it evaluated.
Exam. Can't tell from your description if you have gum recession or if gum tissue is detached from underlying tooth/bone. In either scenario you need to be evaluated and, in all probability, treated.