Dear SIR

I am Sidharth Kirti ,Male ,Age 28 years,Weight 72Kg ,Height 5 feet 6 inches from India ,I excercise daily in form of walk and Jog for 45 min, I am vegetarian,I used to take alcohol daily around 3 pegs (60 ml) and smoke mildly(3-4 ) a day for around last 3 years ,now i have left alchohol and smoking completely for last 3 months .I have inactive haemhorriods now and do experienced mild bleeding while passing stool (1-2 times) in an year when my stools are hard but they are under control from last 2 months as i have been taking lot of fibre(in form of salads,fruits,psyllium husk daily)from last 2 months and i do take loads of water(about 2 ltr) in morning before going to toilet two times in morning and i take around 1 ltr water in evening to again go to toilet.In between also i take around 1 litre of water during day.I do have normal bowel movements but have to go two times in morning and 1 time in evening to feel good .

ACTUAL PROBLEM: SIR about 2 and half months back i was taking lot of food outside and I experienced brutual farting sessions(10-20 in 3 hrs) and looseness in stomach in evenings from 5 to 8 pm sometimes with smell ,sometimes not smelly but with lot of sound everyday for about 10-15 days and after going to toilet everything became normal and farting used to stop and then it again used to start at about 5to 8 am in morning and again stopped after going to toilet in morning .It was like a timer attached to farting and flatulence but stools were normal ,no constipation,no pain and all.So i approached local doctor ,first i was given antacids,antiflatulents like omeprazole and antigas like simethicone etc but all of no use . Then I went back to same doctor and he told its a chronic parasitic infection of intestines and he gave me metrindazole and other medicines for five days,after taking those i felt relieved and nothing happened for about 2 months then one day i took food outside and the same symptoms arise again ,so i went to doctor (have to go to another one as old doc has shifted) and he gave me same type of medicine for two days only and i was relieved again ,but again after 2 weeks i experienced same gas attack and then i took course to ornidazole and ofloxacin for 3 days(as self medication) and was relieved, AGAIN AFTER 2 weeks I EXPERIENCED SAME , despite taking hygienic home food and water (from R.O). This time went to doctor and he made same diagnosis of infection and gave me course of Netazoxanide+rabeprazole as i had already taken ornidazole ,I TOOK his medicine but i felt constipated and stomach pain and dysuria after taking this medicine but there was no farting so i stopped taking it after 2 days as my farting was relieved but after one week again the same evening and morning farting is there causing lot of problem as i have to work in evening.
Q1)Please tell me what should i do and what exactly is this diseases ?
Q2)Are these initial symptoms of colon cancer etc?
Q3) WILL Taking so much of these antiparsitic drugs in such short span of time cause serious sideeffects.