Wheelock’s Latin is a great textbook, but it can prove to be a bit difficult to use on your own, especially if you can’t check a lot of your answers! While there are answers for some of the exercises in the back of the book, this isn’t true for those found throughout the chapters.
Thankfully, if you are an independent learner, a teacher, or are homeschooling someone, HarperCollins will happily provide you with an answer key. You have to fill out a simple form to request access to the key; this form can be found here (http://tinyurl.com/wheelockkeyrequest). They do this simply to prevent people in high school or college Latin courses having easy access to the answers. A minor inconvenience to independent learners, but it makes sense.
Best of luck in your studies!