If you had already lost 50 lbs on your own prior to surgery, it is not uncommon for your body to "hold on" to weight before it decides to release it. Especially if you are on a low amount of calories, your body might have gone into starvation mode. I was sleeved on September 27th so a couple of weeks before you and hadn't really lost prior to surgery. But when I hit the 2 1/2 month mark I was definitely stalling. Saw the nutritionist and she said I had to get my calories up from 800-900 up to 1000-1200 because my body was hanging on to the weight for fear of never getting food again. Once I was able to up my calories I have started to lose again. Slow, but at least I am losing. It is hard to get in 1200 calories - I am literally eating something every 2-3 hours. And if you are working out alot you actually need MORE than 1200 calories to not starve your body. Seems weird but that is the science of how it works.
I, too, would suggest that you meet with the nutritionist and get some additional guidance.