Hi!
If you were my patient, I would advise you that if you are 11 weeks on 2/18/12, your conception date would be right around the 17th of December. I am assuming that your due date is based on a first trimester ultrasound. Ultrasounds done in the first trimester are accurate within 5-7 days.
I'm sorry to say so, but your encounters were too close for comfort and I would recommend a DNA test. My suspicion is that you were already pregnant when you took the emergency contraception on the 25th.
There is no evidence to suggest that emergency contraception will cause any harm to a developing fetus. It also won't interfere with an existing pregnancy (it doesn't cause miscarriage). Because your dates are SO close, I don't want to hazard a guess as to who is the father, and would recommend the DNA test.
Good luck!
Dr B
When u put ur due date in this app it gives u a date of conception but wait til u have ur ultrasound cause that will be more accurate
Sorry but the only way to know for sure is a dna test. Your doctor should be able to give you a better idea though at least regarding what the chances are when u took the morning after pill. But I would still get a dna test no matter what the doc says, its to close..