Im on antibiotics cause of some infection, possibly strep, been drinking lots of water, the anti makes me thirsty, did extra water make me lose weight?

Probably not: Drinking extra water will either make you gain weight, if for some reason you aren't removing it all by peeing, or more likely, in people with normal kidneys, will result in neither weight loss nor gain. If you have been eating less from the infection, that could account for the weight loss, or there could be something more concerning going on. YConsult with your physician if it continues.

No; Food in vs Out: All living creatures are open systems, i.e. every atom our physical body is made from keeps changing, some rapidly, some slowly. Thus we eat not just for energy (which has no weight) but for raw material which we break down into small molecules (protects us from outside control) selectively absorb these, use them to rebuild our bodies & also keep tearing down out bodies, Wt is the current balance.