I'd like to jump in here because I also had physical therapy for this exact thing. I was prescribed an anti-inflammatory which helped but the PT was really more beneficial in the long run. Therapy consisted of gentle and repetitive stretches like on this website:
www.sportsinjuryclinic.net/sport-injuries/hip-groin-pain/piriformis-syndrome/stretching-piriformis.
I continued these stretches at home and also found this technique online with one of those large inflated exercise balls. Lie across the ball on your stomach with your feet touching the floor on one side and your arms outstretched in front of you touching the floor to keep you steady. Once you're stable, roll forward a little and then back. How this helps you is if your sciatic nerve is pinched, this slow movement might get it unpinched. This actually gave me immediate relief. Good luck. I hope you feel better.