My boyfriend and i had unprotected sex on the 23rd he did cum inside but i also usually get my period on the 26th, can i get pregnant between those 3 ?

Sure: Anyone having sex without condoms or birth control is at risk of getting pregnant. The days before your cycle is a lower risk time but one can never be sure when ovulation occurs. Use over the counter Plan B if intercourse was within 72 hours to decrease the risk of unplanned pregnancy.

Yes: Unprotected sex in a young girl can lead to pregnancy and infact, more than 50% of pregnancies in the US are unplanned. Use plan B to prevent pregnancy and review your options for contraception to be adequately covered.