I Have Been Just Diagnosed With H. Pylori Infection, What

I have been just diagnosed with H. Pylori infection, what causes this, my doctor never mentioned any ulcers, if this is not cleared can it cause ulcers, Should I stay away from certain foods, my doctor has put me on two antibiotics and changed my apo omeprazole (Omeprazole to Tecta as well as it was not working for me as good as it use to
Thanking you in advanced