Were you able to make contact David? I agree with the others that being honest and apologizing is the best route. I think it's good that you realize what you did was wrong/inappropriate and perhaps you utilize that as you move forward. I can't remember, do you see a counselor or therapist? The fact that you realize that you just say things off the cuff is good, but there are steps you could take to re-learn how to handle yourself in those situations.
I think it's also important to remember that apologies are not always accepted in full. AKA - it's possible that if you did indeed offend your sponsor deeply, they might accept your apology but choose to have you work with a different sponsor. Not saying that is going to happen, but be aware it's a possibility.