bleeding on CD15 😕

Hello ladies - I've been TTC for 3 months with my hubby, since we started my cycles seem to have changed and become very different - and now this month I started using the cbfm and I've stated bleeding (more than spotting, but still light) over the past 2 days - does anyone know what this could be? I'm not meant to of ovulated yet...  so disheartened... please respond if you have experienced anything like this yourself? Thank you x