L.P.
I am so sorry that you have found yourself in this difficult situation. You're right, life does throw us some curve balls sometimes. My heart goes out to you and your family!
IMO, you should probably not have more children. If you happen to get well again, then by all means have more. But right now, while you are very ill and are not sure if you will get better, I think your time would be better spent enjoying the children that you already have. They need you and need to build great memories with you. If you had another baby, much of your time would be spent with that new baby (and worrying about that baby during your pregnancy). Not to mention that the new baby would likely have to grow up never really knowing his/her mom. Plus, it would be much harder for your husband to raise 3 children on his own than it would be to raise 2.
Just enjoy the time that you have with your boys. I wish that no family had to suffer this type of injustice. All the best to all of you.
L.