@pattysyarns I see nobody has chimed in here. Even if you are tolerating the antibiotics well, they are taking a toll on your body, and the infection is also still active, so you probably won't "naturally " gain weight.
What most of us have to do is eat in ways that don't come naturally. High-calorie nutritious foods, frequent small meals and/or snacks, protein shakes of smoothies...think peanut butter on crackers or on apples, cheese, a hand full of nuts, full-fat dairy products, baked potatoes or sweet potatoes with butter, ice cream, steak - whatever appeals. It took over a year after I finished antibiotics before I got back near my pre-illness weight. Now my primary is encouraging me to stay near the top of my weight range in case the MAC comes back.
Sue