The reason I ask is that i would basically like to know if it is possible for an infection to enter the system even if it was mild, and how long bacteria would be in the blood?

I had two infections in one go, both treated with antibiotics, I was still feeling ill so I had some blood tests including Full Blood Count and Blood Cultures among other tests, the tests all came back perfectly clear. But I have been getting worse and I am now getting told that it is all psychological.

However, I would like to know how long a person can have blood infection/sepsis? Would having had antibiotics mask the test results?