I went through the same thing. I did wear slightly baggy clothes in HS because of it hiding my body plus I dont like anything tight. Everyone knew of my health issues, plus I was out a lot due to being sick. Did I get picked on? Yes. Did I have alot of friends? No. I had 2 friends in school and lost one to backstabbing before high school ended. As far as clothes, you dont have to wear really baggy clothes, just one size larger than what you wear normally. Loose but fitted. You can try different jeans on to see what makes your butt look good. I perfer LEI jeans, but honestly my butt didnt show up until after HS. As far as small boobs (join the club), wonderbras are great and so are lightly padded bras. Nothin too padded or over the top. They make some that are padded in the bottom of the cup so when you wear it they push up what you naturally have, looks more natural.
I know things have changed since I've been in school (10yrs now...geez I feel old lol) but regardless kids are mean. Bottom line & they go after who they see as "weak". My advice to you so know who you are as a person & stick to that. Dont do things just to fit in. I know being popular and what not seems like everything now but when you leave high school no one cares. That's right, no one cares who was popular, who was prom king/queen, etc. It doesnt matter after the drama that is high school. Just know who you are as a person, what you believe in, stick to your morals, & keep yourself healthy so you can get through high school & go on to bigger and better things afterwards. Then in 10 yrs you can go to your HS Reunion looking younger than everyone else (thanks to CF) lol!
I hope that helps you.