Pregnant or not pregnant????

So last month I had my period for 7 days :/. On the last day of my period (no blood just cramping) I had sex with my SO he came in me and I was worried so I took the morning after pill and was prescribed back on the pill only for it to cause problems 
(headaches) so I went off them. 
I can't take any other contraceptive medication / method as it will give me serve headaches. :/
Moving forward this week I got my period and it only lasted 3 days. 
And then yesterday My SO and I had sex and he came in me again
My question is it possible for me to fall pregnant?