I go to the gym about 4-5 days a week and I always see plenty of people of various body types, but I don't judge people negatively based on their body size/weight. I'm at the gym for the sole purpose of working out and to stay in shape. I don't have the time of day to look around and make judgements of other people - that's not why I'm there.
I know that it's easier said than done, but you need to try to just forget about other people and what they might think (I said "might" because I doubt that the average person even pays much attention to you or to other people anyways. They are focused on what they're doing instead). Have confidence in yourself! Know that a complete stranger's opinion of you doesn't matter. You should be going to the gym because YOU want to be there.
After all, you're not at the gym for THEM; you're at the gym for YOU