Post-implantation Cramps

I am posting anonymously as I haven't told anyone that I am pregnant yet. I have been having painful cramps starting 10 days post-ovulation. This is now day 8 of cramps. It feels like period cramps, but even the long ones don't last more than a minute or two before going away, and they are often hours apart. So they are infrequent, but some of them are quite painful, and cause nausea. I am wondering if anyone else experienced this, but then went on to have a healthy pregnancy.

My period was due 2 days ago, I got a positive pregnancy test this morning.