Another Positive

So just for the hell of it I took another OPK cuz I was having a tightness and swollen feeling in my uterus and ovaries and this is what I got. Are you kidding me? What is going on with my body. I know that you can use OPKs as pregnancy tests but they aren't very reliable. Not to mention I'm only 5DPO so implantation is highly unlikely. But in my research I did find that a few sites said that implantation can occur at 3DPO which I had a very big temp dip at. I don't have crosshairs yet but if I put in fake temps for the next two days I get solid crosshairs on CD15. (Here's my chart http://www.fertilityfriend.com/home/19c4c9 ) I don't know what to think. I give up. I already had 3 positives! Why another one?