You could just call him and explain it plainly that you got scared. You've never been in this situation before and didn't know to handle but his text made you realize you been a fool and you are going to do better and open to receiving all he has to offer. Just give him complete honesty is all I got.
you've clearly articulated exactly what the issue is on your part here--which is a great thing since you are aware of what your actions did--i think you need to meet with him face to face and tell him exactly what you just shared with us..