Have been diagnosed with gad and major depression, been doing well but had affair with married man, now symptoms are back. is this as result of affair?

Affairs with people: who cannot be there for you in a real ongoing relationship, are stressful and depressing, so yes, they may have re-triggered your symptoms. Listen to the sone "Soon" (Sung by Reba McEntire) and find a way to take back your life. Psychotherapy may be needed in addition to the simple 3 minute music therapy relayed in that great country song.