I had sex with a guy one month. Got my period. Im 98% sure it was a true period. Had sex with the boyfriend I have now after and now I'm pregnant. How do I know who's it is. Im scared... Please don't be rude. I had a blood test and it says according to my hcg level I was only so far along... Which made it my boyfriends. The doctors say the ultrasounds match up with my lmp even though my baby measures slightly bigger than average... If it's the first guys will my baby come a month earlier than my due date for sure or can it be a month late? ;/

It is possible while not common to have a period ( first one) and be pregnant. As noted conception dates are estimates, so there is no way to tell. You have no choice at this point, but to wait and have a DNA test done with the child is born, Read this site, we get people in this situation almost every day.

I have been in the same situation with my first child. There is a two week window. Look at dates I know it's really stressful but try not to stress too much if anything do a DNA test you can by them at a drug store after the baby is born I know long time to wait! But it's best for you and child also let your boyfriend know what's going on so he's not blinded by situation I let mine know and he stuck by me:) hope it goes good for you and don't stress!!

The likelihood is its your current boyfriend's. However there is no way to say with certainty until a paternity test can be done afterbirth.

And why do you think we would be rude?