Why didn’t I get pregnant ?

So in the month of January starting from the 5th because I had just got off my period to the 18th of the month I had my side man nut in me about 6 times and then I had another man (don’t judge) do it twice and today February 2 I got my period and I took a pregnancy test before and they were all negative, I already had a baby so I don’t know what it could be? Am I not fertile no more or should I go to my OBGYN to get it checked out?