This is totally normal. The brainwashing does not go away the moment you realize it's not the truth, that takes time. The organization has had you for thirty years, they have impacted and molded your thinking, probably in ways you don't even yet realize yet, because it is so much a part of who you are. This is the nature of cult mind control.
It's going to be uncomfortable for a while, but it does get better with time. As you guessed, thus is where people tend to go running back to the organization because it feels comfortable, but that is just a temporary band aid to a huge problem, it doesn't solve any problems because the doubts and unhappiness are still going to be there for them.
Think of this as a character building moment. You need to trust yourself that you made the right decision, even if it feels uncomfortable in the moment. The organization teaches a kind of learned helplessness, this idea that you can't trust your own thoughts and mind (because that's coming from Satan don't you know). Don't believe it, it's a way to make people afraid to think for themselves. Trust that it will get easier in time and that making it through the fear will make you a stronger and better person.
. So I feel like im starting my life again at 31yo. I passed up going to medical school when I was in my early 20s because Armageddon was so close. Now, it’s too late to start down that path.
I call BS on this. It's never too late, and 31 may seem old to you, but from my perspective you are just a baby. I was forty five when I left, I've had a whole other life since then. I am recovering from two serious medical issues and restarted my business last year at 60 and I still have plans and goals, so don't limit yourself. People are living longer these days and staying healthy and productive longer as well. I won't lie and say it will be easy, but don't limit yourself. If you can make it through leaving a cult, why not take that newly found strength and wisdom and apply it to medical school? You might be even more successful as a mature individual.