What Causes Difficulty In Breathing And Buring In Nose?

Hi , i caught a strong cold Three weeks ago and and strong caughing , and a lot of saliva in mouth and vomiting somtimes , i took pills and ect and i felt better , but then i got some other troubles, i start hard to breath and like i feel can't breath well especially through my nose and i get afraid and shocked coz of it and feel my hands shaking and legs too and that scares me .. i once went to hospital and made me oxygen and they checked my breathing rythm and heart beats on screen too and they said it's fine and i felt better after that owygen and that sth they've added with oxygen i don't know what's it , then with days i felt better ..ect however it comes from time to time and then i find my stomach full of gas and ect i checked a doctor told me it's that " thick colon " or sth like that , and get treatment but i didn't take only one packet , but what bothers me the most is the lack of breath and hard to breath , and feel my nose burns somtimes inside and like i can't breath easily by nose and i freak out , so please could you explain to me what's going on with me ?