Unfortunately many of us backslide. And backslide badly, and it takes awhile to recover from the damage. But you CAN. So DO it.
You have to STOP this, and you have to apologize at some point, but you don't want to grovel. It's a fine line. Make it simple. If he talks....you're going to have to listen, and TAKE IT....it might not be pleasant. But don't let it discourage you, either. It's just a snapshot of the moment, it isn't the whole ball of wax....and you CAN recover from it. People recover from these things all the time. The key is DON'T DO IT AGAIN. DON'T GIVE YOURSELF AN OUT.
Rob--this isn't what we do here. We SAVE marriages.