Cholinergic urticaria is something that is not uncommon.
This could be due to :
Exercise
Hot baths/showers
Fever
Occlusive dressings
Eating spicy foods
Emotional stress
Based on your message, I feel that emotional stress could be the fundamental reason while there could be one more other reasons.
First and foremost stop assuming and worrying when you feel sweaty or body getting hot. When you start getting emotional you fail to think practically that would lead to unwanted complications.
Next Steps
You need to work on two things now. Consult a doctor /dermatologist for the urticaria issue and take preventive treatment. Then see a Counsellor to help you manage your anxiety and stress. God bless.