Hello , So I Just Found Out Today 10-28-15 That

hello , so i just found out today 10-28-15 that i was pregnant with my 2 child . i had sex with man ( will call him L ) and me and L had unprotected sex around 10-10-15 . i took a pregnancy test on 10-16-15 it said negative . 10-19-15 i had unprotected sex with another man (will call him C) . well then 10-21-15 i had unprotected sex again with man L . today 10-28-15 i found out i was pregnant ! I was with man L for a few months period was on track and never got pregnant , all a sudden i have sex with man C i get pregnant with 2nd time . "which hes my first childs dad" not sure how far along i am nomore then 2weeks i think. i took a early response test . my last cycle was over with 10-1-15 i want to say ? Not sure rather or not man C is my 2nd babys dad or man L is my babys dad . would like to know your HONEST opinion on it . * not to mention that when i first meet man C i got pregnant within a few weeks of knowing him i had our first born . then we break up and havent unprotected sex since atleast over 100 days and all a sudden we have unprotected sex again and found out i was pregant the next week . keep in mind i also had sex with man L . I would also like to know how early can a pregnancy test pop up a positive ? how long does it take ... few days , weeks ... ? and also when the OBGYN does a ultrasound and tell you due date and how many wks & days you are mean that lets say she says oh your 5 weeks 2 days and i count back on the calander and it says the day i slept with man L . does that mean my un born child is his baby ? please give me more info .