I'm currently on CD 15 of a cycle which was 27 days last month (first month between my first two periods off the pill). I've been taking OPKs for the last few days, it was very faint earlier in the week as it was it this stage last month, but the line never got darker and now just taken one and it's negative. I'm expecting to ov around now. Is it possible that I've just not ovulated this month?