I had intercourse 2 days before my periods were due. I did get this period I then got a light period in 3 weeks and had intercourse the day after this stopped. I now am pregnant have done 3 and have all came up poss when was more likely to conceive though I am unsure? My doctor thinks I might be around 9 weeks is this possible?

Most likely time would be from the intercourse after your period as this is the most likely time for ovulation to occur. While possible, ovulating just before or during a period is not the norm. A pregnancy is usually dated from the last period, because the day of exact conception is not usually known.

Is the 9 weeks about when your last period was? When you have an ultrasound they will check baby's stage of development and may alter the date slightly.

If you are concerned about paternity, one may be more likely than the other, but with just a few weeks difference, you would need a DNA test to know for sure.