Can you always tell when you ovulate?

I can usually tell by my body signs rather than an opk when I am ovulating. I get really watery discharge and ovarian pain for 2-3 days.

I’m just wondering for anyone else that can tell, is it possible it’s not always as pronounced every month? I got ‘positive’ opk’s but my body didn’t show any obvious signs that it usually does. I know it’s possible to get positive opk’s but not actually ovulate.