help :(

So I was going out with this guy.. was amazing every time we hung out and I was really falling for him. Turns out he's still with his baby momma. But we had a quickie one time and didn't use protection. 
I'm on birth control, but I honestly never take it at the same time, just everyday. And I'm so scared now that I found out the truth.. 😞 am I safe? Or should consider getting the day after?