Opk/ovulation

I used answer opks this cycle and ive been getting very faint lines the past couple days. This afternoon it was darker but not as dark as control. Im also starting to cramp alot now. Should i go ahead and say im ovulating or should i test again tonight to see if it gets darker? We are bding tonight and did last night. Just kinda wondering if it has to be as darker or darker or is it possible body doesnt surge high enough to get a positive?