I got a very positive OPK (the line is so dark it's almost black!) - does this mean I'm ovulating NOW or will?

I'm confused - I got an "almost" positive this morning at 7:30am and when I tested this afternoon at 5pm it was definitely positive! It went positive as I was peeing on it but does that mean I'm currently ovulating or will I be tomorrow? My hubbie and I have been BD'ing (and everything else that comes with TTC) every other day since CD10 (currently on CD23) and daily yesterday, today and will tomorrow. How do I know when my 14-day luteal phase is up to test? Help!