Typhoid Fever. Typhoid again and again?

Hi Doctors, Few days back I was diagnosed with typhoid and it was the 3rd time I was diagnosed with typhoid and 2nd time in past 10 months. So, my doctor suggested me to have a blood culture test and in that test, there were no signs of typhoid (I took medicine before going for test). So, my doctor gave me a single tablet for typhoid and told me to have it for 15 days as I was having typhoid like symptoms. Now I have completed my 15 days course and I am completely fine but still there some doubts in my mind. 1. I feel very weak sometimes and I feel out of breath very fast. How can I recover from this? 2. Why my both the test results differ? 3. Why I am having typhoid again and again? Please let me know these things as I am very curios to know. Thanks in advance.