If i get an infection while on immunosuppresants after an organ transplant will i need to go to hospital because it could kill me, even a cold?

Immunosuppression: You could probably get away with seeing your primary care physician locally if you don't feel that bad. They can determine at that time based on your labs, vital signs and overall state of health if you need to be hospitalized or just be precribed antibiotics as an outpatient. If you feel horrible skip the middle man and go to the hospital because a severe infection can be lethal.