Please help me potty train my daughter!!!?

I have a 2 1/2 year old daughter. I have been trying to potty train her for about 6 months now... but she acts like it is killing her to go on the potty! I don't force it because I don't want her to become afraid of the potty; but I don't know how else to go about this situation. I have tried sticker charts, a piece of candy (like an M&M or skittle), simply clapping and "hooray"ing, compairing her to "other big girls like Dora" that go on the potty... etc etc etc... but she simply doesn't want to go! She screams at the top of her lungs as if she is terrified or in pain! I know I should just wait until she is ready... but perhaps there is something else I can do to make her think it's fun to go on the potty?? Any ideas would be wonderful!! THANK YOU!