Re: IF you have unprotected sex the day right after your period had just barely ended
If you are looking for someone to tell you that you absolutely cannot possibly be pregnant, we can't. I know someone who had sex ON her period, using a condom. Her son is now 14. I know someone else who had two full periods WHILE she was pregnant. So, anything is possible.
Like I said on your other posts, 5 days before your period is due, take a test. Then, get some form of birth control and use it along with condoms. That way, you are very, very unlikely to become pregnant and you won't have to deal with this stress and these questions.
Oh, and unless your BF has been tested recently (before he had sex with you, after he had sex with other girls) he could still have an STD. I know people who have had STDs with no symptoms and passed them on to innocent people. So, it might be a good idea for you to have an STD screening too.