Okay I am so confused about these darn ovulation tests...HELP!??

Okay my husband and I have been trying to conceive for a while now ( about 5 months). For the last few months I have been using ovulation tests. Now, I have never had a problem with before. I have been using them regularly every 3-4 days regardless of a positive or negative result. Now, here is the thing....Exactly two weeks ago tomorrow I got a super strong positive....it stayed like this for two days, my hubby and I did our thing and then I went back to getting negatives....perfectly normal right?? Well for some odd reason this morning I thought just for kicks I'm going take one....I was sure it would be negative being that I ovulated two weeks ago...but no...it was a super strong positive!! What the heck?!?! How can I get a positive ovulation test two weeks ago..then a bunch of negatives and another + two weeks later....what gives?? I know I dont have PCOS or anything like that...Why would they do thi