My last menstrual period was march 9 and I was with my boyfriend all of march having sex about every other day. I had sex on april 11th with another guy at 2am and tested positive pregnant april 16th at 2:30 pm. Then on april 17th was told by vaginal ultrasound I was 5 1/2 week pregnant. Then on the 24th of april had a yolk sac and heart rate of 106. Is there any possible way I became pregnant from guy on 11th of April?