I'm skinny, 5'2 99 lbs, two weeks ago I restarted working out more frequently, I've been doing abs for a very long time though. Last September I started working out then stopped end of November.  November my stomach suddenly started sticking out more ,I couldn't figure out why. I measured myself and I my stomach/waist was 25/27 in the morning 27/29 at night. I measured again last week and I was at 26/28 in the morning, 27/29 after dinner. It has been consistently like this for the past week. Today I did a 45 minute total body workout, and my stomach is huge!! It's at 27/30 and I haven't even eaten dinner yet!! I did eat after and efore the workout, granola with lactose-free milk, banana, toast with nut butter, hard boiled egg, half a protein bar, salad, granola bar, and whole nutrition smoothie from jamba juice. I usually eat more than that before dinner, I just woke up later today. I don't understand why my stomach is sticking out more before dinner than it does after! I don't feel full, I feel kinda airy and jsut big. My stomachs hard and when I flex ther's not much fat to grab, maybe a centimeter or two. I'm gassy, but when I saw my doctor she said I wasn't very constipated. I do not have regular bowel movements though. My goal IS to gain weight, meanining muscle, so I do eat quit a bit, but my stomach size is worse than ever. I eat super healthy, drink a lot of water, I do get anxiety sometimes, I've read on other forums that that may be a factor,  and I normally don't have that much fruit in a day which may be a factor...More background info, I used to weigh more then I lost about 15 lbs and am trying to gain it back, I liked the way my body looked before. Yes, I had a lot more muscle before, and my stomach before I lost was around 27/29 at night, maybe take some depending on the day. So yes, it's really irritating me that my stomach is bigger when I weigh less, I would like to know why and if it's possible, how to make it stop.