Changing In front of SO

So me and my fiancé live together and we have for over a year. I see myself as a bigger girl (pic attached) and he’s pretty lean. I have gotten to where I don’t like to take my shirt off during sex or change in front of him. He’s never said anything but positive things about my body but I just can not do it. Has anyone else dealt with this? And if so, how did you overcome it? I’ve been working on living a healthier lifestyle. I just feel like he deserves so much better.