Advice.

Have a cavity on the right side of the mouth. developing one on the left side too as all my teeth are yellow and I see black marks on the tooth on the left, I have brushed pretty poorly my life and ate a vast majority of sweets, I now take care of my teeth but it seems that the damage has already been done and that it’s irreversible. I am generally concerned and don’t know what to do. as I am petrified of going to a doctor, (I’m not a dentist/doctor etc just a normal person.)