I Am A 19 Year Old Girl, The Last Day

I am a 19 year old girl, the last day of my last period was Aug 14,2015 it is now Nov 17! I took 5 home pregnancy tests and 2 blood tests to come back negative! My sister had the same problem but ended up having a cyst on her ovary. Could that be what is wrong with me or could it be my hormones wacked out? Also are there vitamins to help balance hormones such as at walgreens or any drug store without a prescription needed? Thank you for taking your time to read and answer my questions