Hi!! I, too, am a 28-year-old mom of 3. Mine are 6, 3, and 16 months. They're a handful, but I still find time to eat and pack on the pounds.
My doctors have ruled out PCOS (I have trouble breastfeeding and at one point we suspected maybe a hormone imbalance/PCOS was to blame, but nope), so I feel like it's just my fault, and I have no self discipline. My mother has hypothyroid and has since her early 20's, so I'm always terrified I'm going to develop it, as well. My last blood panel was a year ago, so I'm going to have another one done, soon.
I agree, I'd like to be a "cute" pregnant mom, with my (eventual) other pregnancies. Right now I just feel... Ick. And I also want to be a good example to my kids, you know? None of them have a weight problem, but I feel like it's only a matter of time, because my husband and I aren't the greatest examples.