If you take prilosec for 14 days its suppose to help for the next 3-4 months. (for me it helped for only 1-2 months) So if you start today you can still finish before pesach, and it should help you at least to get trough yom tov.
“I live with heartburn all year!! Tums really works for me. For Pesach, you have to ask a shaila?”
There are kosher for passover Tums with an hechsher of the KAJ.