They are very similar to AF cramps. I had really strong ovulation cramps and my AF like cramping began just a day or two after ovulation. I got my BFP 9dpo and am now 21dpo and still have some minor cramping. I'll also say with my first pregnancy, I kept waiting and waiting for AF to arrive before testing because I was having all of my normal AF symptoms at the time, but it never arrived and I ended up testing almost 2 weeks after AF should have arrived. My best advice is to chart down your symptoms day by day and really try and notice any changes happening to your body. I knew this last cycle was the one just by listening to my body. I'll try and bump it up so you can browse through it. It was very helpful for me!
There's a really awesome thread on here that has pages and pages of ladies' dpo symptoms. You'll be surprised at how many had similar cramps like AF during their early pregnancies!