Again, wish I had an answer to the overthinking part. All I do is seem to look for answers as often as I can.
It must be something to do with the way our brains are currently wired. We just cannot accept not having an answer - just like you are trying to find an endpoint for your symptoms. This is not just you, I do it - and most of the others that have been active on this forum would also have done in.
This is how we work as humans. If there is something wrong, we NEED an answer. Even if there isn't one, we still keep looking to the point that it becomes an obsession.
You are nothing short of normal my friend.