You can go to www.babymed.com and type your info in and it'll calculate it for you.

Or beginning January? I'm not sure when I exactly got pregnant

You're 3 weeks behind me and my last period was December 8. So I'd say end December.

k @jlf240

Just use a calendar and count back the weeks.

@jlf240, could it have been the middle of Dec or end of Dec

If you're 27 weeks now, you got pregnant in December.