Dodging the bullet is always hard to do if you've always accepted what is just asked of you no matter what. Here's something you said though that I found interesting.
"People know to come to me because they know I'll say yes. People have come to me asking favors and even though I really didn't want to do them or couldn't do them, but I did. I guess I'm just really afraid to say no to people."
Here's how I understand that. You say that your afraid that people won't like you if you don't help them correct? Here's the bonus question though. Are these people coming to you for help because they are your friends or are they just anyone that come up to you for help? I understand your fears of rejection, but sooner or later, you'll have to face it, it's a fact of life, and to tell the truth, it's not as bad as you might think.
Here's the good side to the story though. You are realizing what is going on in your life, as many many many many before you have not. Hopefully since you see what's going on, with a little push from us, you can concentrate a little more on yourself, and a little less on everyone else. Granted, its good to help out once in a while, but not every oppertunity that you get, you'll overwork yourself (like I did)
Talk to ya later
Dobby