So I need help when do you guys think I got pregnantt

So I had my son may 10th 2019 it’s bad I felt really horny right after I had him like literally after I was wanting to have sex so bad I even had stitches. I waited about 2 weeks & had sex I don’t think he came in me .. I’m not sure soooo June 9th comes around my period finally came back it was heavy as EVER lasted till the 18th or 19th we had sex while I had that heavy ass period I know disgusting 🤦🏽‍♀️ July 4th comes around I realize I’m feeling nauseous I don’t want to really drink but I did had to literally hold my nose when I did.. so we have sex that night the next morning I woke up I spotted it was very pink light pink. I was like🤷🏽‍♀️🤷🏽‍♀️🤷🏽‍♀️ maybe the sex was to rough I go to my post PARTYNEXTDOOR appointment I’m suppose to get my birth control the implant I go on the 16 or 17th they took a pregnancy test it turned out negative and a blood test negative. I’m confused when I got pregnant I found out I was pregnant august found out I was having twins in September 😊 lol my due date is March 29th !!!