Multiple positive ovulation tests?

I started testing on the 6th of January (way too early I fear I will miss it) but anyway I had a very light line like I normally get & kept that tiny light line until the 10th when I got an almost positive (CD 13) my tests were full on positives the 11th, 12th, 13th & 14th... tonight it looked lighter more like the test I took on the 10th, what causes this? & when did I ovulate? it's not PCOS I've never done this before... I miscarried in October & am fairly new to this whole trying for a baby haha.