How can I stop overthinking feeling like I am sometimes trapped in my physical body and I panic?

Hello! Thank you so much for your question. I can tell this has been very distressing for you and I am glad you have sought some help and information.

The experience you are describing is something you definitely are not alone with. What you have described is essentially components of what we would call "hyperawareness OCD" (specifically "sensorimotor OCD") as well as components of what we call "depersonalization" and these often go hand in hand. Now before I continue let me start by saying I am not offering a diagnosis, rather simply saying that you have described elements of these and am going to offer you some insight.

Depersonalization is most often described as an experience where you detach from your body/mind and feel as though you aren't real, which can often lead to questioning your existence as you mentioned. While some of what you described was being trapped IN your body and mind (though you did mention questioning being in your body at one point), I would still say much of your experience falls into this category. When this occurs and you begin to (anxiously) question your existence, it can create a habit of hyperawareness as though your mind is suddenly checking in with your body more than it needs to to prove that you are real.

Sensorimotor OCD is where you are mindful of what is going on in your body, but the awareness of that awareness becomes disturbing. This is also known as the "mindfulness hijack". Essentially, your process of mindfulness and awareness, which are usually desirable and helpful, becomes oversensitive and acute to the point that it creates anxiety and panic.

So in a nutshell... you have these moments of anxiety where you question your reality and existence which causes your mind to become hyperaware of your existence and bodily sensations which creates even more anxiety causing an obsessive thought spiral.

The difficult part about this is that layers develop. It starts with the initial hyperawareness of things like body movements, this leads to thoughts/fears that you will never escape the pattern of hyperawareness and be able to be present, and then you develop a hyperawareness around your hyperawareness (essentially checking to see if the problem is still present) because you're desperate to get rid of it. Tricky, right??

Now for solutions... Honestly the best solution is therapy with a professional who is trained in Exposure and Response Prevention (ERP) therapy and/or Acceptance and Commitment Therapy (ACT). Both of those can prove incredibly useful in gaining insight into the root of your anxiety as well as learning how to face your thoughts and accept your awareness as it is without needing to judge them/it or needing to react and with the understanding that it is not going to hurt you. 

You are not alone in this, and I hope this will help you have more understanding and figure out your next steps!