I was around seven weeks pregnant with our youngest DD on our 2013 trip. Found out we were expecting literally a couple weeks before the trip. I was fortunate to not have bad morning sickness during the trip, just occasional nausea and more so fatigue than anything else which probably also had a lot to do with the demands of keeping up with four other kiddos along with being in my mid 30's instead of in my 20's like I was with my prior pregnancies. I definitely wasn't up to doing any night shows/fireworks in the parks, after 8:30pm I had to be in bed or I was a complete grouch, lol. I sat out of several specific rides that DH and the kids enjoyed without me (TOT, Everest, Space Mtn, Big Thunder); but there were a few 'mid level' rides that I still did (Soarin, Test Track, the Safari, Toy Story Mania, Pirates) in addition to the really tame ones (IASW, Dumbo, Nemo, etc.) I also cancelled me and DH's 'plans' to indulge in a couple of those Grey Goose citrus slushies in the WS at Epcot. He's such a sweetheart that he refused to get one since I couldn't. So the Grey Goose slushy at Epcot, Expedition Everest at AK (DD8 is obsessed with riding this again so I agreed to be her riding buddy on this one), and Fantasmic at HS are on my personal must do list for this next trip, lol!
But I think you would be fine. Pace yourself, get acquainted with bathroom locations in each park, stay hydrated, and take breaks when needed. Good luck!