Due date wrong??

Is it possible for doctors to get my due date wrong? Perhaps like way wrong? Lol I’m only asking bc I’m 24 weeks and I am HUGE. Baby even feels huge in there. I’m terrified for what I will look like at 30+ weeks or if my poor little body can even make it to that long! It is my third pregnancy, so I get that you show sooner the more pregnancies you have. Let me just give you a little run down...

So I had my last period in July last year. Like July 17th-ish. I’ve had irregular periods in the past but I started taking hormone supps that helped me out tremendously. I ran out around June though. August comes and I missed my period. I took a pregnancy test late august and it was negative. I took another test two weeks later and still negative. September rolls around and still no period. At this point I didn’t even consider retesting, as I just thought it had something to do with my hormones. So I got back on my hormone supplements in hopes that period will come. October comes and still nothing. I did start getting mild cramps so I thought it would come and then I start getting sick like everything I ate just hurt my stomach and would make me throw up. So I was convinced (and pls don’t make fun of me lol) that I had a mold illness. 😳 ANYWAYS. My mom tells me to just retest before I do anything else so I do and BOOM. Big fat positive sign. I wasn’t able to see a dr bc I wasn’t on insurance at the time and due to me moving, I had to wait a month or two to be approved and receive my insurance card. I ended up going to the emergency room in December bc I was spotting which has never happened with my last pregnancies so it was a bit of a scare. There I was told that I was 11 weeks. Didn’t see an OB until January at around 16 weeks and they couldn’t seem to figure out my exact due date. It went from June 30th and now June 25th. Im wondering if maybe I was pregnant in august all along which would make me further than I am but is that even possible??