i had sex on my period i stopped early.

What do you mean you stopped early? Your period ended early? 

If that is the case then I think its quite unlikely that the reason your period ended early is pregnancy. For you to get pregnant, you need to have sex on, or near (3 days ish) ovulation. Ovulation is when your body releases an egg. Every month an egg is released from your ovaries. The egg then travels through your reproductive system, and if it is not fertilized leaves your body (this when your period happens). The blood from your period is the lining of your uterus. This lining builds up naturally to protect your child, should the egg become fertilized. Ovulation occurs roughly in the middle of your periods. So about 2 weeks before your period occurs. The egg doesn't live forever, if it has not been fertilized in about 3 days after ovulation, it dies. Sperm can live for about 3 days. so if you have sex 3 days before the egg is released, the egg could become fertilized. Same with if  you have sex 3 days after the egg is released. This 6 day time frame doesn't over lap your period. So it is almost impossible to get pregnant if you have sex during your period.

However, if you think you are pregnant, you should talk to somebody like a doctor who is a little more educated in the matter than I. You can call Planned Parenthood at 1800-230-PLAN. They will have be able to help you better than anyone. (You may need to look up a number for Planned Parenthood in your area, I'm not sure how recent that number is)