czelek

the first stall out of the gate at around the three-week mark (although it comes earlier for some, later for others) is extremely common. We even have a name for it "the three-week stall". Almost everyone has that. In fact, if you do a search on this site for it, you'll find over 17,000 posts on it. And I am NOT kidding. Just stick to your plan and stay off the scale for a few days, and the stall will break. Usually takes 1-3 weeks. And know that it's likely the first of many stalls. It's a natural part of losing weight. I think your body just has to stop and recalibrate once in a while.
constipation is also a very common issue after weight loss surgery. It's probably due to the high protein diet plus some of the supplements (iron and calcium supplements are the usual culprits). A lot of us have to take daily Miralax or stool softeners to keep on top of it. Other things that might help - magnesium tablets, prunes, Smooth Move tea. You might have to experiment to see what works for you. I take a capful of Miralax every morning and have been doing it for eight years.
does the dizziness occur when you stand up? If so, it's probably orthostatic hypotension - also very common early after surgery - and it eventually goes away. Until then, just stand up SLOWLY.
Protein shakes also count as liquids, so it may not be as difficult as you think to hit your fluid goals.
the first few weeks are a challenge, but. you'll soon have all this behind you!!