pregnancy

I'm 16 years old and my boyfriend cummed before we had sex but it was unprotected .. that month I got my period but it was lighter than usual and i thought it could have been caused by stress because I was so worried if I was going to get it or not. still the past months my period has been a little lighter but I still have a good amount of blood. I also started eating less meat and cheese that month and lost weight from that as well so I don't know if that could have affected my period. I have taken 4 tests even after 3 months and all came out negative so I'm sure I'm okay no serious symptoms at all either , I was just worried because I read things online that some girls were pregnant and took tests and they still came out negative. When I was worried about being pregnant it was the worst few weeks of my life .. it was 4 months ago that I had the unprotected sex also