OPK's picture in comments

Rebecca
So I'm currently taking clomid 50mg days 2-6 my first round I got pregnant but unfortunately led to a chemical I'm not back on them and got advised to use OPK's this time round so I have done the only problem I have is the line started getting a bit darker then boom nothing the day after I'm on cycle day 18 can anyone help please? I'm a bit confused tia x