You are at the famous 3 week stall. About 3 weeks post ops folks go into this stall were they either stop losing or some even gain a pound or 2. Your body is trying to play catch up from on the drastic changes it has had. I nearly lost my mind during this stall because it did not make since to me. I was only eating 500-600calories " how can I not lose weight". All though I research and read that others experience this stall it still was hard to take. Just keep tracking, exercising, and drinking. You will get through it. As far as the 8 oz of yogurt goes... I would measure it just so you don't stretch things. I hope this helps.