Self conscious

So... I’m trying to loose weight, I’m a sophomore in high school and I’m pretty big, and so I’m embarrassed to do certain things, but I decided to get out of my comfort zone and got a membership at the local planet fitness, and at first I felt great because I’ll have s personal trainer and a schedule designed for me to reach my summer goals, but the thing is, a lot of people from my grade go, and now that I’m thinking about it, and I’m too embarrassed about them watching me exercise, which is stupid but I’m really self conscious, specially at my size, but my mom says I shouldn’t let them interfere with my goals, because I really want to loose the weight, but I’m still embarrassed to do it, and I don’t want to work out at 1 am just because there’s no one there. So what is your advice if you have any, please, I really want this, but I’m too embarrassed to do it