Cavities? or worse?

this may be kind of long so bear with me please... um like 2 years i bit into a rice crispie treat and broke a tiny peice of the backside of my tooth off.. not a bid deal you couldnt see it so i didnt worry about it...fast forward to last year...it started hurting bad to the point where i couldnt chew with that tooth and sometimes if i was brushing my teeth it would bleed alot and hurt if i hit it with the bristles of my toothbrush....now the same tooth on the other side hurts(its not broken) it doesnt hurt to chew with it but its really sensitive to cold... the other night i took my dog for a walk and it was cold out and just from breathing with my mouth open it hurt for like 30 minutes...or when i smoke i can feel it...i know i need to go to the dentist but i dont have insurance(or i would have gone a while ago) but im wondering are thse cavaties or something worse...they also hurt when i eat sweets. im so scared im gonna have to get my teeth pulled please help if you know anything