I have degenerative discs and have had two children. I also had a back surgery when I was 20. I was very worried, as you are now. I am not going to say it will be easy, but it will be worth it.
It is hard to say exactly what pain issues you will deal with because everyone is affected so differently with their pregnancies and back issues. My back problems have been much more prevelant since having my first and deciding we would like one more has been a difficult decision.
In my case, the third trimester was when my back would start shifting. Massage and chiropractic care helped me through that. Labor and delivery is what I really worried about, but had to pain (well, extra pain!) or extra difficulty due to my back. However, the biggest problems came after the babies were born. Especially with my second. My back shifted extremely out of place. It was one of the hardest times for me because I had a young child and a baby that needed me and I could not easily move. After a couple months of physical therapy and a cortisone injection things improved and I have not had any other major issues in the 2+ years since.
Recently, since we are preparing to try for a third, I asked my back doctor about the big trouble coming after. He said hormones might play a role since they are changing so much. I also believe it is because the muscles that have to work extra hard to support a spine with DDD are stretched out and weak.
Okay, so I have been thinking about what I should do to hopefully not have a repeat of what happened after my second. Maybe some of it will help you.
First, try to be in good physical condition really focusing on core strength. I was in pretty good shape that way and still had major issues. I would just hate to see how much worse they would have been had I no strength or stability in my core. Work on the exercises your doctor, therapist, chiroprator give you. Stretching has made a huge difference in my back functionality.
Second, enlist the help of a chiropractor or physical therapist from the beginning. I plan on going back to my chiropractor for most of the next pregnacy in hopes that it will help keep things relaxed and flowing better. I am not going to wait for any pain or shift to really set in. My chiropractor did have me see the massage therapist a lot last time and I am convinced that played a major role in things calming down. So a regular massage is on my list of things to do during the next pregnancy.
Third, try to get in to a physical therapist after delivery. I plan to do that as I believe their techniques will help the body adjust to all the post-pregnancy changes.
I am nervous about going into this again, and I am not getting any younger, which is not in my favor when it comes to a bad back, but my husband and I have felt strongly that our family is not quite complete. My hope and prayer is that these things will help it run more smoothly, but I know the blessing that will come to us will be so worth it. There is nothing like the feeling of delivering your baby and then holding him/her in your arms.
I wish you the best in your decision. I know you posted this a few months ago, but I hope it helps. As I said before everyones' body is different. Best luck in finding what works for you.