Reason for it. Me best solution for it!

I am getting fluffy poop every day since one year I drink lot of water approx 3 liters a day and eat fruits in diet but i constantly attacked by infections in my digestive system and i had Mesenteric and sub centric LYMPHADNOPATHY measure approx 0.5 mm when I get infection I got to doctor he gives antibiotics for 5 days they infection will be cured but every day i get fluffy stools. And i am suffering from reoccurring infection I think it was 4th time in this 3 months but i need a permanent solution for it please any tell explain me what is happening in my bowl and i am feeling pain in lymph nodes suddenly and pain disappear suddenly doctor given some pain killers and Told shrinking of lymph nodes take a lot of time he give some probiotics also they also don't work please provide me best solution for it