Hi and welcome to Healthcare Magic. Thanks for your question...
From the symptoms you describe you seem to be having a nocturnal panic attack
. Panic attacks can sometimes occur in the night and the kind of symptoms and the timing which you describe seem to be indicative of a nocturnal panic attack. Also, when people have panic attacks repeatedly they can also develop a sense of apprehension or fear of getting another attack... This is called 'anticipatory anxiety', which is what you seem to be experiencing.
You have mentioned that you have been thoroughly investigated and that all medical tests have come out as normal. You have also mentioned that you are already seeing a therapist and are on medication. I suggest that you discuss with your therapist to see whether the dosage of your medication needs to be increased or whether you would benefit from any additional psychotherapy
All the best.
-Dr. Jonas Sundarakumar