How Should Cold, Cough, Throat Pain With Nose Blockage Be Treated?

Namasthe Sir! Recently, I travelled from vizag to hyderabad (in india) by train in 3rd A.C. Coach. After getting down in the morning, i got severe Cold and it also resulted in cough. Earlier, i used to have cold and cough frequently, but not this severely. Now it is not so severe but more than the previous affects. this time, along with cold, I got some Severe Throat pain too. My brother who is also a doctor suggested to use Combiflam for throat pain, and throat pain is reduced. But the cough is increasing and cold is also not being controlled. The other problem that i have when i suffer from cold is that my Nose will be almost blocked, and in deep sleep, i will take breathe with mouth instead of nose, unknowingly... which causes thirst during nights and my lips and tongue become dry due to movement of air. I am not taking any kind of chilled liquids or foods. So today i went to Apollo Pharmacy and the retailer sold me AZAX-500 and I just now consumed one tablet. I want to ask you whether is it advisable to use that antibiotic for my problem. I am also suffering from increased sneezing. Kindly help me and suggest me the necessary precautions to avoid cold in my life time so that i will strictly be adhered to them because, more problem with having cold is blocking of nasal cavities with (in telugu it is called KAPHAM) which makes it difficult for me to breathe.