Omeprazole and weight gain?

I didn't notice that, but I was not taking it for as long as you have been. As a generality, much drug-side-effect weight gain comes through one of these routes:

* Higher appetite so portion creep.
* Water retention.
* Fatigue, possibly very subtle, that reduces daily life activity (think fidgeting, automatic things like hair/nails growth rate, body temperature or responses of body temperature to conditions so maybe feeling cold more often, etc.). These sound tiny, but can be in the low hundreds of calories daily, potentially.

The situation may not be perfectible, unfortunately. Still, to some extent, there are mitigation strategies that can theoretically help.

* Appetite may be countered by careful calorie counting (and maybe experimenting with different eating patterns to find better satiation).
* Water retention can gradually creep on, over a surprisingly long period, but there's hope that if fat loss is happening and not showing up on the scale, it will eventually peek out from behind the water-weight clouds on the scale. (If you suspect an unhealthful level of continuing water retention, talk with your doctor).
* Fatigue-induced lower calorie burn is tough, but if there's any way to improve sleep quality/quantity, reduce other-source stress (which adds to fatigue), or increase mild-intensity movement in daily life, that can be a way to push back a bit.

I don't mean to sound unsympathetic, because I do understand (have experienced some of this from other drug regimens or health conditions myself). For myself, when dealing with obstacles, I like to parse out some of the potential underlying mechanisms, and experiment with changing things that might help. To me, that feels more empowering, like I'm taking control of the situation rather than letting it control me, even in cases where my experiments may not all be successful. I understand, though, that we're all wired differently, when it comes to what works.

Hoping you find some solutions!