I take 4 benadryl (diphenhydramine) to sleep and im 16 will it harm me?

Yes: First, you are still a minor, an adult should be overlooking your drug intake. Second, you exceeded the recommended amount of benadryl (diphenhydramine) for a single dose, 50 mg max, that's 2 tabs, if that's not working, it means you developed tolerance to the drug, and you may need more to induce sleep, hence the need to look for something else. See your doctor for evaluation of your insomnia, good luck