If you are playing high end soccer you know the drill. Low fat and low carbs and a ton of cardio will drop that 20lbs in a hurry. Your club program has to be full of very low body fat guys who can help you. I'm surprised you don't have a trainer or a coach all over you for being a chunky keeper. You're short for a modern keeper and only being really fit will keep you on an elite path.
As far as the girl goes, she's more interested in how you treat her and how confident you act. The way you're fussing over 20lbs is hardly going to convince her you're "the man".