jackmyster

hey over the summer i started to ge this throbbing ache in my back teeth both top and bottom. i tried everythin to relieve the pain. Finally the pain went away by itself. it didnt start hurting until november of this year again. i looked into my mouth and notcied that i could see dark spots on the top of my teeh. The throbbing has just recently come back full throttle and i am unable to eat food. i know they are cavities but how can i tell if ill need a filling or a root canal. i am 18 years old and the last time i was at the dentist was 8 years ago???? Please help me?????///