CD 15 today anyone else?

Hello ladies. I'm on CD 15 today and I have very light pink spotting this morning when I went to do my opk. Negative for LH surge. I've had lots of low back pain and cramping. Started opks yesterday. Anyone else get this cramping before o? I've never really kept track of all this before it would be great to have some cycle buddies to help me understand this all. I have 3 children so far but this is my first time actively ttc.