I had sex on the 2nd of September and had my period on the 7th. Could I be pregnant?

While very unlikely, there is a slim posibility. It does happen, when you have sex close to a period, that if pregnant, you may still have that next period. It is more common to have a short lighter period.

Really if there is doubt, need to wait to see if you get the next one. Really doubt you are, but you did ask if you could be, so yes you could be.