TTC #2 weird periods, BBT?

I've been on BCP for 11 years, my period was always irregular on it, sometimes heavy &painful, sometimes barel there. This period seems to be barely there. Normally day 1 I'd soak at least 3 tampons, sry tmi :/ this time I'm on day 1 or day 2, I had light bright pink/red spotting and the same today, since my periods aren't consistent Is my best bet to try to figure out when I ovulate by going off my bbt? I'm buying a thermometer tomorrow anyways but is that going to be my main way of telling? I don't want to try ovulation sticks cuz they're just way too expensive. Almost 60$ for 20 days supply in Vancouver Canada.