There is a difference from the adrenaline you feel when you are excited as compared to the adrenaline you feel when your fight or flight response kicks it. Further, with the UFC, I imagine you probably had a fight instinct
, here you are more likely experiencing a flight instinct.
I know I am not a doctor, but it does really sound like anxiety. I really hope that you find comfort and peace. Do remember that it can be a long road, but it will end in success.