So I am 28 weeks pregnant. On 4/11 an incident happened and I has unprotected sex with this guy. My boyfriend and I were having constant sex for a few months unprotected and him ejaculation inside me. On 5/13 I went to the hospital and had an ultrasound and was told I was 6 weeks and 6 days pregnant. My ultrasound dates have matched up since until I was 18 weeks and it put me two.days earlier. My due date is December 29th. I'm confused on how conception and your LMP work. Is this my boyfriends baby or that guys. I'm worried sick, someone told me since there's only 4 weeks between those dates its my boyfriends, but what if they were wrong. like I said I'm unfamiliar with how the last missed period works with calculating it. Please help me out and no negative feedback please. I can't be at peace with myself. I'm hoping my boyfriends, please let me know if I've left any info out.