Can you pinpoint exactly what part is confusing? If not, can you identify the spot where it stopped making sense? You don't know that you aren't the only one in the class who is struggling. The fear of being the only one shouldn't be the reason why you don't ask for help. You don't need to prove that you are a good student. Explain to your teacher that you've been trying to do the assignments and are just completely lost. Approach it with an attitude that you are ready to learn and will do whatever it takes, for instance, "I've been struggling with some of the material and I was wondering if I could meet with you sometime one on one to talk about a plan for how I can catch up. What time is good for you?" Then when you actually meet, express your concerns and desire to learn the material, ask if he/she has any tips for you, etc. Then schedule a follow up meeting to discuss how it went.

In my experience, teacher will be a lot more open to helping you if you approach them on your own terms and are committed to learning. A lot of teachers look for that initiative. Good luck!