Birth Control and Ovulation

I've been on birth control for about 5 or 6 years now. I switched from the pill to the patch about a year ago. 
​I know I'm not supposed to ovulate but I experience an increase in my sex drive around the time my calculations say I should be ovulating. I have no idea how to check and see if I am ovulating. 
​I am not TTC in fact I'm trying to not get pregnant. But I am overweight and I know BC doesn't work as well when overweight. 
​How can I tell if I am in fact ovulating? And if I'm not why is there an increase in my sex drive?