Quoteat church this preacher pushed me out of the way, and didn't say he was sorry. but im used to that! I'm so small its hard to even see me.
Well, here's my two cents if you want it....I know this will come off blunt because of it being typed words, but I mean for it to help.
This sounds to me like you have a problem with your self-esteem. People push you around, but do you ever say anything to them? Do you ever stand up for yourself? You're words seem to indicate that you don't if you're so used to being invisible and you pretend that it doesn't bother you, when clearly it does or you wouldn't have asked about dealing with rudeness.
Being assertive doesn't mean being a demanding person and you do not have to return rudeness in kind in order to be assertive. What it means is that you simply state your needs. Most people don't mean to physically push past someone, they may just be preoccupied, however if you simply say "Excuse me" in a plain tone, they will apologize for knocking into you (if they're not a waste of air). Most of the time, a person will not be assertive because they feel that they don't really deserve the same politeness that other people get, for one reason or another.
Because you feel this way about yourself, other people will pick up on it and treat you accordingly. That's why it's so easy for those false friends of yours to laugh at you, tell you that you're not important, and treat you like garbage. Assertiveness is a sign of self-confidence and even if you aren't that confident, if you act as though you are you may just develop some self-confidence on your own. But whether or not you're as confident as you portray, the fact that you are showing confidence will often cause others to treat you better than if you show no confidence. Beware that this may cause some of those false friends to walk away from you completely. It will be because they've realized that they can't get away with walking all over you anymore. It might sting at first, but you're really much better off without toxic people in your life. People that like you for you will be happy to see your self-esteem rise and will continue to encourage your personal growth.
Here's an exercise that can help your self-esteem. Think of some things that you are good at. And I mean really do it, don't be like "Well, I'm not that good." Give yourself credit. Or we'll do it if you won't, but it might not work as well. What are the things you like to do? Do you go to school? What types of things are you interested in? I'm sure we'll find things to praise you on when we get to know you better!