It's difficult for me to answer your question as to what you should do while pregnant. I got mine when I delivered my daughter--it was like someone took a knife and cut/sliced me across the stomach on the inside--and it wasn't discovered until she was 2.5 years old. Yes, I had pain. But the pain came and went and didn't cause me undue pain until the very end. My doctor couldn't find where the pain was coming from. It got to the point where I'd be driving my car to work in downtown traffic and I'd get a sudden, searing, knifelike pain that would slice across my stomach. The pain was so intense that I would almost black out. Finally my doctor sent me to a surgeon. He had me stand, poked his finger into my belly button, and asked if that hurt. Hurt? He just about made me pass out! Yeah, THAT was the spot.
The surgery went well, and I was up and about pretty fast. They used laproscopy, I believe, to do it. But I have a high pain tolerance level and heal pretty fast, so my results might not be the same as yours.
Oh, and mine didn't stick out; it was inside. In fact, by the time the surgeon went in to fix it, it was pretty bad. He said 2.5 years was a bit long to wait to have it fixed. I just looked at him and said my doctor couldn't find it. He said that is actually very common for the type of umbilical hernia I had.
So with yours sticking out and being pregnant, I can only imagine the pain. But I really wonder if they'll do anything about it until after the baby's born, just because they don't like doing surgery while the baby's still inside. I also wonder if the hernia will change your birthing options--like having to have a C-section--just because of the intense pushing that occurs with a natural childbirth? It could cause it to become worse or, in the worst-case scenario, break open.
I would talk to my OB/GYN and look at all the options. If it's better to wait until it's time for baby's arrival to do something about the hernia, then I would try to have it taken care of right after her delivery. Maybe if you have a C-section the surgeon could be there and fix the hernia right away? That would be the best-case scenario.