@good times,
Run Away! This is a very bad thing; she is using you.
She is going to hurt you badly. There is no way that this relationship can work. I am dead serious... you should get out and never see her again. In fact, you should be angry at her for using you this way.
1. You are a teenager. Your teen-aged years are a time for you to figure out what it means to be an adult without having the responsibilities yet. You don't need to support yourself. Your parents still take care of you and are responsible for keeping you from making bad decisions. A sexual relationship should be with someone who is a peer.. so you can share this part of your lives together.
2. This woman is an adult. She is in a completely different part of life from you. She is independent; either in college or working. She is responsible for her own mistakes.
She she views you as a child (the way that you would view someone who is 11).
An adult knows how to manipulate a teenager. This is why what she is doing is illegal (she could be arrested for having sex with you). And think of it.. she will dump you, there is no way a 22 year old is going to want to date someone in high school. And it will hurt... and at that time you will realize what an awful thing she is doing to you.
My advice is for you to talk to an adult about this, you will be hurt, and having an adult who knows what is happening to you will help.