A great way to check for understanding is to go back through your textbook. A lot of people underestimate the power of the textbook. However, it's the best source. Another thing to do is quizlet. It's a great source to quiz yourself on questions and vocabulary words. One last thing to make sure you are understanding concepts is explaining everything (and I mean everything) to someone in your household who can ask you questions (Why? Where? When? Explain, etc.). Also, give yourself grace! You are human and can only retain so much at a time.