No Problem
If small children, seniors, people with handicaps and everyone else you see there every day can enjoy themselves, so can you. The "E" rides have appropriate warnings and there is so much else. In some ways, you may enjoy yourself more as taking things slower, you can see more.
There are plenty of seats around for frequent breaks, and yes, keep the water going. I would suggest building up your walking before you go (as anyone would benefit from that).
I would also check at the spa's (like Grand Floridian) to see if they have a special pregnancy massage. May be a nice treat.
I think that Epcot would be best as the way it is layed out, you can move a little then rest, move a little, then get in the AC. AK will probably be most difficult and you may want to put that off for another time.
I personally think the hardest visit is with 1-3 year olds...but that's just me.