If U Was Having Normal Periods And Juz August 14

If u was having normal periods and juz august 14 suppose to but the 23 wen off 27 went to doctor get check for pegnant I wasn't so 27 I had sex bf condom popped I been of the pill for a month or so then we had sex couple more tymes in end of august but I had sex with another guy sept 4 he pulled out that's was the only tyme I went to the doctor in the end of sept they said I was 5 weeks and 4 days and said I got pg sept 5 so who most likey the father