To ask the obvious question, have you talked with your physician? And had updated blood and other tests to see why you're losing weight?
And if you're on hrt, folks (generally but not universally) tend to have two different reactions. Some put on weight and fat, often a lot, and some lose weight and add some fat (obvious places). As they say, it's in the factors of your body, physiology and genes, but don't go down a course of not exercising and eating excessively. First, seek real answers then consider a nutrionist to help you add the weight.
The last thing you really need, and want if it happens, is to gain a lot of weight to discover you can't lose it and it threatens your health. It's far harder to lose excess weight/fat than gain it. You can control the weight gain, but rarely the weight loss.