Irregular period after getting off birth control (ortho Evra).

This was my first month off of my birth control (ortho evra). Before getting on birth control my periods were always normal. This is the first time my period has been irregular. My period was 8 days late and lasted 3 1/2 days instead of the normal 7. I know that birth control can cause you to have a irregular period for a few months but I am mainly wondering if im ovulating and if I am does that mean im ovulating later than normal? Any other ladies gone or going through this? Advise? I bought ovulation test for this cycle but with my cycle being off im not sure when I should start doing them... if anyone else is going through this I would love a cycle problem buddy. =]