After intercourse las night i bled a lot . bright red . it stopped about 10 minutes later. could i be pregnant?

Possibly: Many reasons for bleeding after sex exist. It always makes sense to check with your doctor to assess and find a treatment as needed. If pregnant or near your period, sex can cause bleeding or bring on your period a bit earlier than usual, but this is not something you should rely on. More serious reasons include infections, cervical polyps, vaginal tears, and cervical cancer and pre-cancer.