implantation bleeding or period?

Am
Hey, I'm on my second cycle of clomid 50mg.  My cycles always last 27/28 days and I always have heavier periods.  The last cycle was very light and lasted 7 days, Aunt Flo is scheduled to arrive April 21st.  For the past couple of days I've had bleeding. I'm not sure if it's implantation bleeding or if it's me starting my period over a week early. I haven't had much cramping, if I have it's been very minor. I called my obgyn and she started me on progesterone 200mg, if I don't start my period by next Friday they will do blood tests.  Have any of you had the clomid mess up your cycle? I'm praying that this is implantation bleeding and that this month will be our month finally! Please say some prayers.