2nd Pregnancy and terrified

Hi guys.. so I took a pregnancy test today and it came out positive clear as day... I told baby’s dad and that’s the only person who knows right now. We lost a baby earlier this year in April... I was about 20 or 21 weeks I can’t remember right now. But the day before I lost my baby me and baby’s dad were having sex ( this is what makes me feel it’s my fault)... we were having sex and right after I started getting really bad lower back pains... they got worse no matter how I tried to lay, walk, stretch it just got worse. We went to hospital.. mind you I was at the point where I was literally crying in pain. Couldn’t even sit still.. regardless me obviously being in so much pain even at hospital it took them about 30 minutes to do a bunch of paper work and ask me questions before getting me any help... when I got to the hospital room the nurse treated me as if I was overreacting.. this was the first pregnancy so I didn’t know what contractions felt like. Long story short they ended up telling me I probably pulled a back muscle during intercourse.. as I was sitting in the room back still hurting I felt nauseous.. and threw up and at the same time I threw up I felt a hush of liquid come out of me... I called nurse in . I thought it was pee I didn’t know so I told her I peed. I also told her it felt like a really hard gush.. I sat on the toilet after and I experienced a bit of blood as well as mucus looking stuff. Told nurse . She looked at it and said a bit of spotting is normal in pregnancy ... after I threw up the back pains stopped. And I got sent home... when I woke up that morning I woke up to blood literally everywhere rushed to the hospital and found out baby had passed... the doctor told me when they checked the ultra sound there was no fluid so apparently my water broke the night before and I wasn’t aware.. I also was already starting to dilate... they say they don’t know what went wrong.. my pregnancy was healthy.. now I’m pregnant again and I have so many thoughts and fears running through my head... I just wish I knew what went wrong.. what’s wrong with my body. Will it happen again.. I’m so scared and have literally nobody to talk to that will understand me..