Bothered by looking chubby and thick at normal weight

Hey all - as a girl who's 5'7 and 120 pounds, I know my weight is actually rather low. The odd thing is, my stomach has always stuck out since I was at 110, and with my recent weight gain it's only gotten more obvious. I can tell my upper legs have softened and thickened out too, and I am just not a fan of how I look and feel.

This is likely a body composition issue, but I really wonder how it could get this bad that I look so much heavier than my actual weight? While I never played sports regularly, it's not like I was completely sedentary. Just feeling discouraged because I don't think I'd be able to do enough exercise to fix it "the good way". Weight loss has been the only thing that I've been able to do.