The first day of my last period was Dec 21.10. My cycle is usually 30-31 days. I slept with the guy I was seeing Jan 1st and either Jan 3rd or Jan 4th. Then I slept with my ex bf Jan 8th. I did a first response pregnancy test Jan 19th in the evening - negative. I did another test Jan 26th in the evening- negative. Then another on the 29th that came out positive.
A DNA test is the only way to know who the father would be. Sperm can live up to 5-7 days in the vagina. I'm sorry! You can get a DNA test while pregnant (which carries risks) or you can wait until they are born.
I would suggest getting to the doctor to get a due date and to see how far along you are. Still those dates are pretty close together so you'll deffinately need a DNA test to confirm paternity. Good luck. *in the same boat*