How can I know if my level of chronic stress is dangerous or not? There are just minor symptoms.

Yes. Ongoing stress affects the immune system, raises cortisol levels, can raise blood pressure, increases incidences of ulcers, reduces well being, and more. Practicing relaxation and meditation can help. With severe stress, psychological treatment is advised.
See your doctor. Stress can be associated with causing an increase in your blood pressure or an increase in cortisol levels, which can contribute to the development of diabetes, heart disease, and other things you may not feel. See your doctor for a checkup.