I am currently breastfeeding and on Asacol HD and Prednisone(was 40 mg but down to 25 now). The first time I was put on prednisone I thought maybe my milk supply went down but I wasn't sure because other things were going on as well. My little guy is 19 months old and eats regular food with BM as a supplement in the AM and PM and whenever he asks for it(not often anymore). I agree with one of the previous posts and the suggestions she gave. I was worried as well when I started the meds but I couldn't be so sick and care for my child as well. I feel great now and I am on a very slow taper of the pred. I am hoping symptoms do not come back like they did the last time we tapered.
Great job nursing your baby! It is one of the best things I have ever done...I love it! I get a lot of looks these days now that I am still nursing a toddler but I don't care. We will stop when he is ready. My decision to continue nursing while on meds was due to the benefits of breast milk over the possible negative side effects of the meds....so far my little guy has not had any bad side effects. My boy is also allergic to cows milk in any form so it just makes sense to give him my real milk.
Good luck!!!