The loss you're seeing now is part of a cycle that started with surgery and your initial weight loss. Those hairs went into shock and stopped growing until a few months later they fall out. But the next stage starts right away, which is those hairs start growing again in your scalp. The sucky part is you will lose new shocked hairs due to the rapid weight loss, so your hair will be going through this cycle until your weight stabilizes. There isn't anything you are doing wrong or missing out on to stop it. Get all your Protein and then wait it out. This too shall pass!