Brief Answer:
Follow Dietitian and Physical trainer stringently, gets adjusted over time.

Detailed Answer:
Hi.
Thanks for your query.
To recapitulate: Male/45 - Pre-gastric bypass was 106 kg and now 80 kg in postop 4th month - urge to eat every hours - was insulin dependent and now only on metformin 500 - mas liquid you are taking is 1.5 liters, urine still yellowish, not feeling thirsty - afraid that weight may increase ....

Good to know that you have lost 5 more kg since Nov 2015.
This itself suggest that you are on the right tract, insulin stopped, only on metformin minimum dose, lost 5 more kg, I hope the pain in the cough muscles have gone.
Since it is months post-op, you can have more water to make the urine dilute.
Feeling hungry but not thirsty, a bit difficult to have and understand. You have to take more water to avoid kidney stones in future.
Getting hungry and urge to eat every 2 hours if the craving one develops and can settle over the time. Since you are conscious about this, I am sure you will have a proper control as you have understood the importance of it.

If the blood sugars are within normal range with metformin, I think you should not worry about the weight gain till you follow the diet and exercises properly.
It takes time to get adjusted to the new homeostasis physically and psychologically. And I am sure about it to be achieved.

So stop worrying, you will be fine.
I am sure you must have a follow-up with your Surgical team, the Dietitian, the exercise trainer, their opinion, interactions and guidance will hep you further in all regards.

I hope this answer helps you, please feel free to ask for further relevant queries if you feel that there is a gap of communication.

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