Ambivalent, If you are coming here to just vent, then caution us that you are venting. However, you do appear to be stuck when it comes to that receipt. When I discovered the receipts that my xh had in his vehicle, I confronted him about it and yes, it was during the holiday season. Once, I knew for sure what he was doing out on the street, it put my mind at ease because I wasn't sitting around "assuming" and doing the stinking thinking routine. Of course, I plotted my course and did some stupid stuff along the way before I found this Forum...but I was able to end the obsessing over those pieces of paper because I finally got the answers to that piece of the puzzle.
It's your call if you think you can wait until after the holidays, but I do think your health is going to take a toll w/knowing about the receipt and not confronting/asking him about it.
Just my two cents.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.