My fingers lock up if i bend them after being straight(bend at the top joint, middle joint locks, seems to distend). what is it? how do i treat it?

Locking fingers: You should prob see an ortho doc for X-rays and exam. It sounds like a "Trigger Digit" (TD) however you're on the young side to have this prob. TD usually causes severe tenderness if you press hard at base of digit palm side.

Trigger finger: Generally, locking of the fingers or thumbs are caused by trigger fingers. This is a benign condition in which the tendon becomes entrapped around a structure called the A1 pulley. If this is painful, an injection or surgery can improve the symptoms. If this is not painful, you can live with this as long as you have full range of motion and full function. Anti-inflammatory meds, finger splint