I am not sure that this is the right forem for this question but I will answer anyway. I had the same problem when I was your age. The irregular periods are probably from just being a teenager. The clots that you are talking about are normal. They result from bleeding heavily and fast. The blood oxygenates so fast that it forms chunks. They kind of feel like meat but believe me its blood. Your headaches are most likely from being dehydrated. You are loosing a lot of blood and moisture from your body and need to drink water to replace that lose. I advise you to tell your parents that you need to see a gynocologist. He will probrably put you on medication that will shorten and lighten your periods. Remember, if you feel like there is anything wrong going on with your body you should consult a physician. Good Luck and God bless.