Opk's!!! 😳

So I have been chatting since Feb 2015 and since November I have been using opk's, to help. It is confusing me though, as most months they are positive for 2-3 days! Then after I seem to get luteal symptoms immediately after! So I am finding it hard to pin point ovulation😬, and any idea how long after 2nd/third day ovulation is taking place? Sometimes I get negatives in between too, any ideas?