Help i'm scared to go to the pool(well anywhere in public for that matter)?

I'm 17 and im about 70 lbs overweight. since summer has come and the pool opened, my boyfriend has been bugging me to go to the pool with him. He really cares about me and i love to spend time with him and do things he likes to do, but this is very very hard for me. since i've been overweight my entire life i've had a lot of time to be bullied and tormented. going out in public sometimes is very hard for me. i cant even exercise in the gym without thinking everyone is judging me. one time at the gym these 2 girls from my high school got on treadmills on either side of me and talked about me like i wasn't even there. since then i stopped going. how am i supposed to exercise and help myself when other people are always doing this to me. when this happens it usually stays on my mind for a very long time and i get very depressed. so i'm frightened of any situation that involves me being around a lot of people that i know from school. The pool would be a really stressful situation for me because of the amount of skin i would have to show in a bathingsuit. i usually wear t shirts and jeans all the time because i don't want to make myself an easy target for teasers.the graphics on my shirts are usually something im a part of like marching band. i never wear any cutesie graphic tees because they draw a lot of attention. at the pool i would be showing a lot of areas i have issues with like my arms. i gain most of my weight in my arms and legs and thats what will be showing in the bathing suit. my bathingsuit covers as much as it can. it has a small skirt thing to cover my legs a little. i'm very scared that someone is going to make rude remarks when i'm just minding my own business trying to have fun. my boyfriend would without a doubt defend me (probably knock their lights out) but this still doesn't reverse the fact that someone noticed that i'm overweight and commented about it. this would make my whole week after that hell. i would think about the situation and about the remarks they made. i would be so depressed. im a very nice person and i try to be very kind to everyone. i just really need some advice from people who know what i am going through and how they managed to get over their fears.