I was working out before I got pregnant. Nothing strenuous but trying to build my ability to jog. IM overweight for starters but lost 50lbs before getting pregnant, so I had stamina. Anyway I am 13 weeks oregonstate I haven't done any workouts dice I found out. Yesterday I felt great with no nausea or fatigue so I brisk walked for 30 min. It was surprisingly challenging and after my workout I started to get pressure in my lower abdomen, sort of like when menses is going to start. It scared me. I drank 2ltrs of water yesterday. One before and one after. Has this happened to anybody?