I bought OPKs and HPTs from ebay. I was ready to toss the OPKs out when I didn't get a 2nd line when I was sure I was Oing. I got the line 2 days after I thought I should have O'd and it was a nice dark one. Haven't had a +ve HPT yet from them. AF is due Thursday, so impatiently waiting with a millions -ve HPTs.