Agreed.
It's always best to talk to a health professional whenever your health is involved. It's never a good idea to self-diagnose issues, even if it's something you've had going on before.
Deep Vein Thrombosis (DVT) is potentially life threatening, so not worth taking a risk. While the risk for DVT is highest in the first few days after surgery, it can happen even weeks or months later.
If it's not DVT, I do find it odd that you seem to struggle so much with dehydration and think you really need to double-down on drinking more water and not so much on supplements. Hopefully you're taking a bariatric multivitamin as recommended by your doctor? These typically already have potassium and magnesium, so it seems unlikely to me that you'd need additional supplementation of these particular electrolytes. (I assume that was the rationale for eating bananas and avocados).
Sometimes people that sweat a lot exercising can actually lose too much sodium and cause an electrolyte imbalance since sodium is the primary electrolyte in your sweat. I suspect if you're only 3 weeks out, this is also unlikely.