What is better prolotherapy or steriod shot? i might need one in the pubic symphysis and si joint?

Steroid: I would suggest a steriod shot. Make sure that it is done with xray guidance otherwise it may not be effective.

Prolotherapy: Although a steroid injection may immediately alleviate the pain and inflammation. It does little to strengthen and stabilize the ligament across a joint. If you have chronic ligament sprain then prolotherapy is recommended to strengthen the ligament which would stabilize the joint and, thus, decrease pain. Also there are minimal side effects with prolo as compared to steroid injections. Good luck.