Regrets in Declining a Job Offer

I actually just needed to let this out. So I've been working for my current job for about 1.5 years now and up until like maybe March-May 2023 things were alright for me. In around April I was actually close to getting another job but because of some "red flags" that I felt back then, I decided to decline it and didn't continue with the hiring process. Back then I was like, oh things are okay here where I am so maybe I'm fine here for now (I admit I should't have let my comfort get to me). Then in June/July things started to get awful for me and now I'm always like, god if only I took that job! Maybe I could actually handle those red flags. I'm so stupid. I can't turn back time and I think someone else already took that position (they only needed 1 person to do the job) and it would be embarrassing if I contact the hiring person again (I was actually thinking about doing this, but you know, again, it would be embarrassing). Now I'm rage applying, feeling miserable at my job, and not sure where my future will be heading.

Thanks for reading and not being judgmental!! I really appreciate it.