Not sure why you're feeling sick, but you're not pregnant.
You can ONLY get pregnant if you have vaginal intercourse. Meaning, vagina and penis
If he has ejaculated and then touched your vaginal area, while statistically unlikely, there is a very minute chance of pregnancy. To ease your mind you can purchase an accurate pregnancy test at a dollar store. This would be an awesome opportunity for you to empower yourself. If you are engaging in any behavior that could put you at risk for pregnancy, it would be best for you and your boyfriend to discuss contraception. It is also very common to have irregular periods at 13. Take care of yourself!