Can only omeprazole cure H.pylori ? how long will it takes ? will omeprazole cause drowziness ?

Omeprazole doesn't cause drowsiness at all for all of my family members. Whether it can cure your H. Pylori, it depends on how serious it is. If it's mild to moderate, this single drug can take care of it. Yet if your condition is more severe, then your doctor might have to add antibiotics on top of this med.

No, only omeprazole won't cure H. Pylori. You need a combination of medicines - omeprazole plus 2 antibiotics.

https://www.drugs.com/condition/helicobacter-pylori-infection.html