I had my period on February 8 2012, it lasted 4 days then on the 5th day I slept with my ex but he pulled out. Then my husband called the next day and said he wanted us back together and I slept with him the next day twice a day for 3 weeks and he didn't pull out. I have had two ultrasounds one at 8 weeks and one at 12weeks they both say I conceived around the 21st. What are my chances of being pregnant by my ex?