Advice on the Cambridge website: "Antibiotics are prescribed to treat all kinds of infection, from bronchitis to a septic finger. Always check the underlying medical condition - anyone with a serious infection should not be contemplating weight loss until they are fully recovered."
I'd check either with your doctor or your CDC (if you've found one you like yet) before starting. Amoxicillin is usually a short term thing, right, so even if you can't, it should delay you starting by much!
Good luck