Uh oh, you've discovered a fun outlet. And you can shop in your pjs! I think you'll be thrilled with your online purchase.
I have one credit card I use for online purchases. I don't use it for anything else. Reputable credit card companies will not charge you for purchases you didn't make. Just keep an eye on your charges and you'll be fine. No one is going to steal your identity with your credit card number.
And if you're really paranoid, open a PayPal account. You only give PayPal your credit card number. They process payments for you and never share your credit card information with the vendor.