Hello, i have a very irregular period.i found out i was pregnant at 23 weeks 1 day because of my babys measurements. my doctor saying i conceived sometime in november, but my last period was october 6. i am had a sex encounter on oct 22 could he be?

If that was your only sexual encounter in October and November, then yes that was the sexual encounter that caused the pregnancy. Sometimes it is difficult to estimate the conception just on later measurements and if you found out just at 23 weeks and did not expect it before then most likely the fetus is smaller that usual for the dates which would be consistent with estimating conception later.