Dear Christine:
I'm sorry for your pain, but glad that you chose to ask your DIS family for some help. You are NOT alone.
I agree with most of the others, you will benefit from personal counseling. There is nothing wrong with you that needs to be 'fixed' but a good counselor can give you an objective assessment of your life and offer new and effective coping strategies. You are a great candidate, you see/admit the problem, want a solution, are clearly intelligent and motivated! Just note, you need the right counselor, if you don't 'click' with the first therapist, try again, remeber that they work for you!
Having said that, IMO, (thanks to your honest reporting of who you were, and what you were thinking at that time), you never had a marriage, just a roommate!
And now the roommate has become a lazy roommate!
As in most American homes the wife (especially when she works), works longer and harder by doing most of the domestic chores as well.
Of interest, is your claim of birth control failure twice, IMHO this was a sunconcious attempt on your part to improve the marriage, perhaps by making your H (BTW-why is he still DH, not just H or DR [Dear Roommate?]) into a father with 'real' responsibilities. (Just MHO, YMMV!)
Old school thought was that kids do better in school and life if unhappy parents stick it out. New school data suggests just the opposite, kids (even todlers) aren't fooled by their unhappy parents acting and grow up unhappy, and frequently divorced.
So if your primary concern is your Dear Children get divorced.
However, life is not that simple, and your needs and wants also must be considered. That doesn't make you selfish, just human

!
Can you live with a roomate in a non-intimate situation? (He certainly won't, not forever. Does he get your permission to go out and play? What if he gets a disease? or falls in love with someone else?) Basically, I don't see the current situation being able to last long-term.
Thus as another poster suggested, get yourself prepared.
You need a lawyer to secure your share of his retirement!
What about child support?
Where will you live?
With your past medical history, your medical costs may be much greater than 'average', and coverage (with your prior diagnosis) very hard to get/afford!
Thus along with counseling to give you new options, skills and hopefully strength, you need to consider education for a better job, solo bank accounts, STARTING SOLO CREDIT CARDS NOW to establish a solo credit history, etc.
No path that you choose will be painless or easy, but what I see right now is:
You are unhappy and know you derserve better (you do!),
Are concerned about life after divorce (you should be),
and DH/DR is gonna stray, especially without the intimacy. (meaning even if you wanted it to, this current situation will not continue much longer-so a change is comming)
It is best that you pre-plan these changes as opposed to reacting to them.
I hope this response came across correctly. It was meant to be a warm and supportive expose of the options available to you. I have nothing but respect and good wishes for you.
Hope, Love and Pixie Dust,
Tony