I hate being the nice guy all the time
Why do you not like being the nice guy?
I don't want people to take advantaged of me, I want to stand up to myself.
It is understandable to not want others to take advantage and standing up for yourself and not act like the nice guy. But is is important to be a nice person because other people will respect you more.
I can't take it anymore. I just want revenge.
I believe that revenge shouldn't be the answer, as it can turn you into the villain instead. How about trying to ask these people what they think of you, and why they do these things? Being nice has its perks, and you have to use it well in order to avoid these situations.