Not understanding this

 New to this app..Been taking 2 different brand of ovulation tests one was Answers and 2 of the same clearblue for 2 weeks and each time I get 2 lines and one day the test line shows halfway but not all the way dark but it was lighter one day but it never it dark like the control line or darker but I have symptoms of ovulating all last week. I read that sometimes the levels LH aren't strong enough to detect it and to compare each of the days I take an ovulation test and I notice the difference. But I really need advice on this.