Im ttc after a m/c in November. I started using OPKs on day 9. Im now on day 14 of cycle. I realise that you need two lines on OPK with second line as dark or darker than first. My problem is ive only ever got one line on the OPK? One day I had a very very faint second line. What does this mean? By this stage in my cycle (30 days) should I not be at least showing a second line even if its not as dark as other yet.