They are more expensive but I'd recommend getting the Clear Blue Easy digital test. It shows a happy face if you are ovulating and a circle if you are not. I, too, had a hard time telling from the lines if I was really ovulating but there is no doubt w/ the digital...
Sorry to contradict Kricket212 but I read those two lines are always there and only when you are ovulating does the test line go as dark or darker than the control line. Looking at your temp chart I would say you may have ovulated on Monday or Tuesday. I would keep testing with the OPK just in case and see if you get an as dark or darker test line. Good luck!
I usually get two lines the first day one alittle lighter. Then next day they are usually very close. According to instructions once you get two lines you don't need to continue & I would just start getting busy (BD) You probably are ovulating but concentrating so much on the color of the lines you may miss it. I say when you get those lines just keep going for the next 2-3 days. You don't need to continue because that line probably wont go away untiil you get your AF.