Hey i had sex with my boyfriend on the first day on my period and he didn't use comdon and he came in me can i be pregnant?

Although this timing: Would not be favorable for pregnancy - it is very important to use protection every time you have sex.

Menstruation: Unlikely. During menstruation, there is no fertilized egg and the utetus sheds its lining making it difficult for implantation of the fertilized egg ( if there is one). If you're worried about it, you can do over the counter pregnancy test. Hope this helps.

Very unlikely: If you had unprotected sex on first day of your period it is very very unlikely to cause pregnancy.