If you are 11 weeks pregnant now, that means you got pregnant about nine weeks ago, which would be during the middle of December. Pregnancy is counted from the first day of your last period. Usually, two weeks after your period is when you conceive. The chances are that your ex may be the father. Don't forget that many babies are conceived even when people use condoms. I suggest speaking with your doctor again about it and perhaps looking into a paternity test.