You can keep track of your pledges through your Backed Projects page.
In the active pledges section, you'll be able to see your current live pledges, the amounts you've decided to pledge, the rewards you've selected, and more important details. If you'd like to change a pledge amount or reward selection, just click on the project title next to the corresponding pledge and select edit next to your pledge amount.
The successful pledges section lists all pledges for which you've already been charged. If you selected rewards, you can sort this list by estimated delivery date — and you can even select "Got it!" once rewards arrive.
The unsuccessful pledges section documents all of your pledges that won't be charged, in addition to any pledges that were refunded. This includes projects that were not successfully funded, or pledges that you decided to cancel.