Rapid weight gain

6 1/2 weeks and I am gaining weight it seems at lightning speed. I've already gone from a C to a D cup. Was on vacation for week 4 and 5, didn't know I was pregnant and are like a horse and ate whatever I wanted because I thought I could just come home workout intensely and drop the weight. Well with all the fatigue working out intensely hasn't happend but I am walking a few miles a day. This bloat and weight just make me feel horrible about myself. This is pregnancy #2 and the same rapid weight gain happens with the first one. Just feel big right now.