I wish I would have counted from the beginning. The only way I have to figure it out is a box of tickets I have laying around but it would take forever to count them and check which we won/lost and I would still likely miss some games.
1. Sort the tickets by year and by month and then date within each year.
2. ESPN has the Schedule listed by date (first half & second half). There is a pulldown for Year:http://espn.go.com/mlb/team/schedule/_/name/wsh/washington-nationals
3. You can get your Win-Loss for each season this way.
If a spider can weave a spider web, this can be done without much trouble. Yummmm! Cake!