Conception help!!

I had sex sometime around the second week of October. I do not remember if I had a period at the end of October. Then had what I thought was a period at the end of November and had sex again around dec 11-12. Missed my period at the end of dec. and took a positive test on Jan 3. My 8 week scan was done on Jan 25 and again my 20 week scan was done in April. He then started measuring a week ahead... I just need to know if the october sex could have resulted in this pregnancy or if I'm just wigging out over nothing.