Do a detox. Many times our bodies are holding on to a lot of junk that we pour into it. It always results in bloating and feeling lethargic. So give your body a flush and try drinking only water, cut out dairy, and lay off food high in salt for a week. There are many different methods to detoxify your body. Find one that works for you and you can live with for said time. I try and do this 4 times a year and I am always amazed at how much better my body performs afterward.