First off, I feel for you. You are in a tough situation. We don't want to think it's all about those three little words s-e-x, but at the end of the day, it's part of what we need and desire. Don't feel guilty for that.
Personally, I think you need to make a decision on the two men in your life. You are not being true to them or yourself and it's not going to get any easier or better. Make a choice and stick to it.
If you choose the man you are in love with, maybe you can seek out a sex therapist (or therapist in general). Someone who can help you work through it. He's got to understand that you have needs too and you have been supportive, but there must be some half way point you can meet.
What about other stimulation, would he be willing to satisfy you in other ways? Hey, this is how I look at it, ok fine you have some "problems" in that area, but do something to help me with my own needs. We all make compromises, or at least we should...
I think it's obvious you can't live w/out the sex, or you wouldn't be cheating. I don't want that to sound too harsh, either. I think it's normal and healthy. Women are looked at harsher when it comes to stuff like this and it's not ok or fair. I certainly hope you don't get too much negative feedback from the other mommies either.
Whatever you choose to do, give it some thought and do what is right for YOU. Best of luck.