I've had these - but also had some pink tinges on the loo paper after wiping. My consultant said it could have been a small bleed on the placenta and the pains are bruising internally.
BUT she said it wouldn't last more than 48hrs and it has, so I'm going with her 2nd option which was its just baby moving around on your pelvis, cervix etc. etc.
This one is giving me some almighty wallops on my cervix and pelvis and bladder. I feel very bruised - that's the only way I can explain it now!
I was assured its normal and fine - but do speak to your Dr / Midwife if you are very worried! xxx