Can I take prilosec twice a day? Like every twelve hours?

Varies. The usual adult dosage of prilosec for duodenal ulcer is 20 mg orally once a day for 4 weeks. For other conditions the recommended dose may vary. The usual adult dose for Zollinger-Ellison Syndrome is initial dose of 60 mg orally once a day up to a maximum dose of 360 mg/day (as 120 mg orally 3 times a day). So a more complete history & exam are needed to answer this question for your case.