Me & my boyfriend had say on 13th whiles on my period then we had it again 13 days after my period which was on the 26th of that month. We had unprotected sex on the 26th. Could I be pregnant? What are the chances?

Yes you could, but you will have to wait for your next cycle before taking a test.

Yes, especially since that's when a lot of women ovulate. You'll have to wait until you miss your period and take a test to be sure. I'd use a condom from now on if I were you, and if your going to be consistently having sex the I would seriously look into birth control.