Trying to conceive

I came off bc at the beginning of June I have had three periods my cycles are short I bleed for 4 days and have a period two weeks after the last period ended I used two different period tracker apps on my phone and it says on one app my fertile window is today and on the other app it says it is in two days time I have had sex several times yesterday I am not sure when I'm ovulating as the dates are different can I still get pregnant a few days after sex