Calories - exercise question

Question, I am getting within 100 or so calories per day but when the app subtracts my steps or exercise then it puts me really low some days. I’m in week 7 and am not losing much  I’m at a total of 12 lb. weight loss. I lost 11 of that in the first few weeks and not losing anymore??? I’ve recalculated my macros. But nothing seems to help! I’m following the diet/macros pretty close. I am 47 and have hypothyroidism and don’t have a gallbladder. Would this be the problem? Thanks for any suggestions! 😊