They are looking good Wilsey, hope you been BD'in!! I know they say positive is when the test line is the same or darker than the control line but I've read loads of posts where people said that by them rules, they NEVER had a positive OPK even tho they tested every day and they still got pregnant (so they obviously did ovulate at some point!).
As you said there is always a small level of LH in the system which is why faint lines aren't positive, but maybe some women are more sensitive to certain hormones than others, so that what might not be a strong enough surge for one woman to be able to ovulate may be strong enough for another?? In which case an OPK might show not positive when in fact a woman is about to ovulate? Not saying that's the case, just wondering out loud.
Anywhooooo, some of yours are quite dark, especially the last three. I bet they get darker in a few hours.