I had unprotected sex but I am not sure if pre-ejaculation accured.. if it did how many weeks would I have to wait?

About two weeks after could give you accurate results. However, it is best to wait until you are due for the next period and see what happens. Some women will get a positive result about 10 days past ovulation, but most will need to actually miss a period to have a pregnancy be picked up.

What if I have irregular periods then do I still wait two weeks?

I'd start there... if negative, give it another couple of weeks and try another test. If still negative, it would be unlikely that you are pregnant. Odds are lower anyway if he did not actually ejaculate.

In the meantime, if you are going to continue to engage in sex, be sure to use protection every time. If using condoms, they need to be put on before any entry and most definitely if he withdraws to ejaculate and then wants to reenter. Best to use more than one form of birth control to lower the odds even more.

I'm on birth control and take it like I'm supposed to.. and yes from now on we will be using protection.. I was also thinking about going to take the plan be pill?

If you are taking birth control pills consistently, and he withdrew without ejaculation, odds are pretty low that you would become pregnant. Possible, but not probable. The condom, however, would also give some additional protection beyond pregnancy. If the sex was within the last few days, plan b can be another way to decrease the odds.

Thank you so much for all your help.. and I'm going to but some tomorrow before school.

If it was within 72 hrs you can take the morning sfter pill, buy it from the chemist or speak to your school nurse, or go to your nhs walk in centre. Either way,your school nurse will be helpful and should give you some advise. In future go on the pill, or have some kind of contraception as well as using condoms. Your life is too precious to take risks.