Can't identify my lung disease

I'm 15 year old and five months ago was hospitalized from pneumonia. I felt a lot better after my infection was gone but a week later started hearing noises when i breath like some snoring (i think its called rhonchi). My nose would many times start producing mucus which will most likely go to my lungs and cause me to cough when i breath too deeply and after that i start hearing this rhonchi noises(also some of the mucus goes into my throat and blocks my vocal cords making my voice weird). I also get sick very often. My immune system seems to be weak for some reason. My doctors didn't told me why and how i got pneumonia neither i know but it started with high fever going from 37 to 39°C and after that the cough was getting worse, so if someone could tell me how to prevent it from coming back and what was the reason for it, that would be really great. Also, should i spit the mucus from the lungs and nose or swallow it? I don't have asthma or any allergies for sure because i was going to the doctor for that and they confirmed that theres no allergy or asthma. I have problems with sweating too since i remember myself. Please help me anyone, i was going to doctors a lot and they just keep giving me stupid nasal sprays for congestion which i use when i have cold. I think i said everything so i hope that you will give me helping advice, because i was searchig through the internet for months now and didnt get the answer i need.