postnasal drip and itchy nose

Hi,

Im 30 years old male.
In December I had a bad flu and angina. The doctor gave me some antibiotics.
I took them for 7 days and the angina stoped.
But since then, 2 days after I stopped the antibiotics, the back of my nose (on the nasopharyngeal area) started itching with a permanent post nasal drip.
It has been 6 months now and I still have the same symptoms, along with a sensation of feeling bad.
I went to 2 different doctors. They said its allergies or sinusitis and gave me a spray to clean my nose.
It didn't work and the symptoms keep staying.
I read in some books that it could be a mucous infection due to antibiotics using. So I decided to use a natural antifungal spray named propolise. I started using it yesterday. It made it a little better. But today I used it again and since then I feel bad. My face is like anesthetized, and my nasopharyngeal zone is hurting.

I don't know what to do anymore with this situation, please help me.

PS: I started to have a painful belly too since the last week. I don't know if its related. I keep swallowing the mucus from my nose everyday, maybe its because of that I don't know.

postnasal drip and itchy nose