OPK HELP!

So I had a miscarriage last month (August) and we are tryouts g again this cycle. AF started on 8/16. On CD8 I used the Clesrblue Advanced opk and it came back as High Fertility. This was the same test I used last cycle but it says it's for two months. But anyway. It hasn't changed. Everyday it's high fertility. 6 days now. So I decided that I would buy a new package and I used it and it says low now. So the old one said high and this new one says low. What do you think. I thought it was early to get the high so do you think the test was wrong or what? Last cycle when I got pregnant I ovulated on CD 16 I think.