I did colonoscopies 6 and 2 years ago, hemorrhoids found, haven't treated them. Now, positive FOBT. Shall I have a new colonoscopy? 46 yo.

No. The short answer is not now. Alternate tests, such as CBC with iron studies, repeating occult blood testing with a different kit and eventually a capsule endoscopy only after you completed treatment as started for H pylori gastritis would be advisable. Constipation should be avoided as much as possible. .
Yes. Because hemorrhoids usually cause bright red blood, not positive FOBT. You also need to make sure the blood is not coming from upper gi tract. Consult with your gi specialist.