I know this isn't 'fun' to talk to your parents about, but you really need to have a conversation with them. The symptoms you are describing really could be a number of issues- possibly not even related, and before you treat for a condition, you need to make sure that treating for it will help.
If you feel safe with your parents, and it's more embarrassing, just tell your parents that you need a doctor appointment and get into a doctor for an exam. If you don't feel safe, you can also go to the school nurse and have them assist you in the next steps to take- they can't diagnosis you or give you medication, but they will be able to help you.