How to be around your Ex. without felling awkward..?Advice?

Well I started doing Cross Country for my School, and my ex.Boyfriend is doing football. And I know there different sports, but like it summer we both have practice, and somethings were stuck together in the weight room, and it feels really awkward working out in front of your ex.boyfriend, Think didn't work out the way we wanted, but I still have felling for him I guess?, But still I need shake this silly felling off! Right? I am really in need of an advice! How could I be around him without felling awkward