I had sexton the 12 day of last period would i be pregnant?

Getting close: to the middle of the cycle. So, it is possible. Take a pregnancy test if you miss your period a week after.

Possible: Having intercourse 12 days into your cycle is starting to get close to where your ovulation could be. It's hard to know for sure since I don't know your cycle, but you may want to check with a pregnancy test if your period doesn't come this month. Hope this helps!