as'salaamu alaikum,
May Allah make things easy on you sis and guide and strengthen your emaan.
We will be rewarded for our intentions and our actions, but more so by our intentions. If you do salaah and you do it to impress others than you got the wrong intentions. If you do hijaab so others don't pass judgment on you then your intentions are to please them. Our intentions should be only to please Allah and not care about what others says. Our intentions can change as well, if you started wearing hijaab because of friends, you can change your intentions and keep it on to please Allah.
Ever wonder what is benefit of praying salaah 5 times a day? one of the benefits is that every time you stand before Allah, you start to wonder if you were good or bad. if you have sinned then you feel guilty standing before Allah cause you are sinning. So you can either stop the sins to stand with a clean heart or you can stop the salaah and not worrying about being guilty but continue the sin.
In the same token, i think you should keep the hijab on. You mentioned you have done some bad stuff while you have it on. There are many hijabis out there and actually give islam and other hijabis bad name by the way they act and unislamic stuff they do. When you put the hijab on, you offically become an ambassador to Islam and everyone learns Islam by watching you and your actions, not what you say. You should use this opportunity to make yourself strong inshallah, think that they will judge what Islam is based on how i act and so i should act more islamically, not so as to please them but rather not to give them any bad impression of Islam.
I think what you need is more information about the hijab. It's easier to make a decision when you know more about something. Hijab is a direct command from Allah to protect you and give you modesty. Hijab is more than just a covering, there's inner hijaab and outer hijaab. We have lot of hijabis with outer hijab but who totally lack inner hijab, the adaabs, manners and etiquettes.
Inshallah check it out :)
Requirements of an Islamic Hijaab
http://www.muslimahconnection.com/hi...irements.shtml
P.s.
hijab = full body covering
khimar = head scarf