DADT (Don't Ask Don't Tell) doesn't often work, but it does for some people at least up to a point and I think you have seen a bit of that. Perhaps if your girlfriend isn't overly aware of the details of what you're doing, she won't be so upset? You could ask her about that. Some people imagine the worst if they don't hear the details straight up.
I think it's good that you and she had a heart-to-heart about it all and decided to just negotiate things a day at a time as you are able. And it sounds like you and your boyfriend have already got things figured out pretty well.
Good luck and keep us posted.
Love means never having to say, "Put down that meat cleaver!"