Why Do I Cry So Easily Lately?

lately i have just been crying over things that normally dont effect me. i have alot going on with like ex boyfriends and friends and parents. im 16 yrs old and i have been on depression pills a while back. its like my mom can yell or get smart with me and then out of no where my eyes water and i get really sad and start crying. its not out of control crying its just like a couple tears. its like i cant stop it. my chest starts hurting and then i cry. then after about 3 mins or so i stop and im back to normal. many have told me i am bipolar but i never really got it checked. some said stress could be causing this but i have no idea. but this crying thing seems to be a issue. any answers or suggestions i can do to stop crying? its really starting to annoy me and make me feel like i cant control myself.