So I've been trying to increase my weight for some time but today when I went to the gym to do a leg workout, I weighed myself and I had gone from 130 from the last time I weighed myself to 120. I have been swimming alot lately and I didn't know it was possible to lose this much weight in a period of 4 days, but what should (or can?) I do about this other than eating more because i'm eating around 3000 calories a day.