Hi, I'm twenty one weeks pregnant according to my last ultra sound. I had sex with a guy the 15th of May and then got my period the 19th of May. I always get my period the third Thursday of every month and it was still a normal period lasting 4 to 5 days. That was my last period. I then had sex with another guy, who is my boyfriend, around the end of May and beginning of June. I am really worried that the baby might be to the guy that I had sex with right before my period. Do you think I have anything to worry about? Or do you think for sure that I am pregnant to the guy I had sex with the end of May, beginning of June?

You can't be sure of who the father is when sex was that close together. Only a DNA test will tell you.

The odds are in your favour that baby is your boyfriend's for a few reasons. You had sex right before a period, a possible but not probable time to become pregnant, and you would be farther along if you had become pregnant from the sex on the 15th of May.

The sex with your boyfriend puts you just about right on for being 21 weeks pregnant.

Now, given all of that, as joypulv said, the only way to know for certain would be to have a DNA test done.

OK so the chances of it being to the guy right before period are very slim then? Because it was a regular period lasting the same amount of time as any other period.. and me and him only had sex for like less than a minute haha.

If there was sperm released, it could be 30 seconds or 30 minutes, it wouldn't matter.

As was said, your dates are close enough that it could possibly be either one and DNA testing would be the only way to know for sure.

Ultrasounds are not 100% accurate for dating a pregnancy (although they are the best tool for the job and mid-pregnancy tends to be the most accurate for sizing baby and determining gestation), and a woman can ovulate at times other than the norm (although right before a period is one of the least likely times) but yes, the chances of the other guy being the father are low for the reasons stated.

OK, thanks for the help :) so I really shouldn't have much to be worried about then..