SSRIs like Fluoxetine, Sertraline and Escitalopram can increase gastric acid secretion and can cause heart burn and discomfort in the stomach. This can be minimized by taking medications after taking food to some extent. Eventually, this side effect will fade away over few more weeks.
Next Steps
Try to avoid lying down immediately after meals to prevent acid reflux and try taking a walk post meals.
Health Tips
If gastritis is severe, immediately consult nearest physician.