Weight and relationships

My weight has always been something I’ve struggled with. I can’t remember a time in my life where I wasn’t concerned about it. Even when I was as young as 8 I was scared to go down slides at McDonald’s because I feared I would get stuck. I am now 17 and have tried so many crazy diets, puking or skipping meals, running miles. I can’t seem to lose weight. It’s always been something sensitive to me and I never wanted to draw attention to it, so I made a vow with myself to never date anyone who weighed less than me. But that changed over the summer when I met Brian. Honestly, neither of us were expecting a relationship and now we are happiest we could be. He’s my best friend and boyfriend all in one. But he’s really in shape, and he has a slender build while I’m the opposite. Where he has broad shoulders and slender hips I am the opposite. My gut stretches out and I wouldn’t have a problem with it because I had made some huge strides with body confidence but his family loves to make comments. One day we were watching his siblings while his parents were out he goes to lift me up and I Immediately run to the other side of the kitchen, because I didn’t want to be picked up knowing how much I weighed, and his brother immediately begins to make comments about my weight and how Brian probably doesn’t lift my weight. And then later in the night when we were laying down in the living room watching a movie with the younger kids he beings to make comments about my stomach. Sure Brian punched him both times and made him apologize for these comments but they still sting now. But more recently his mother started making comments. We were at his house on a movie marathon date because of my “lack of movie culture knowledge” when his mother walks in and tells us we’re going swimming with his family. We tell her I have no swimsuit only the PJS I showed up in and she says “oh well you can wear Brian’s swim trunks and I’ll see if I can find a spare top” and as she’s walking away I can hear her talking about how she doubts they will fit me. Now that stung a lot but then she comes back with a sports bra and a few tank tops and says “you can TRY to SQUEEZE into these” as I look through the sizes they are all mediums.. I AM A MEDIUM TOP! I don’t know what to do! I have tried so hard to lose weight and I know I’m chubby I know I’m bigger than him but I wish people wouldn’t make comments! I could really use some advice on this topic!