This is my third period I over the last month in a half. I have blood clots and it seems to keep coming every 11 days. Normally I have a period 1 every three weeks or 20 days so I'm use to it being some what abnormal. I'm 35 years not on birth control I know I don't have a STD, am I premenopausal? At my age? Thank you in advance for any advice.