Why do I keep getting infections after cancer surgery?

Had surgery on the 14th of May, went home 5 days later to me nothing seems wrong or the drs on Saturday morning at midnight, I was having stomach problems, no poop, fever, so my husband took me to the ER, at 1:30am was taking to a room,did some blood work even when I had a transfusion, because of my blood low count,they had to contact my cancer Dr, because they don't deal with what I have, at 3am, starting to get IV and pain medicine at 5 am talking to my Dr in Portland, at 7am, had to put a tube in my nose, transfer me from McMinnville to Portland for 4 days, the day I was released, my tube in my stomach seems infected, so I told my Dr intern, but said it was fine, that afternoon, my Dr assistant came check my tube area took a picture, went home, Friday morning at 4 am, was feeling hot, tube looks infected,called my after hours surgery, called back says go to ER, told my husband, he said it doesn't look infected, at 11am, my Dr called said go to ER, they will take a picture. Went to ER, barely signing the paperwork, was called in at 12:30 pm, the Dr put me on antibiotics, took a picture sent it to my Dr