Just be yourself! Who cares if everyone else has a boyfriend, as long as you're happy with who you are as a person. Look, I thought that because I didn't have a boyfriend and my best friend did that I was a fat and ugly person. Then I found out no one's going to care if you had a boyfriend in 7th, or if you were the prettiest girl in school. All they're going to remember is if you were a good person or not. So don't listen to what other people think of you. If you think good of yourself, everyone one else will see that and respect you for it.
Maintain your self respect. If you are overweight, you should exercise and watch your diet. Don't overdo it. Be honest, care about your hygiene and don't worry about others.