implantation cramping??

Can you tell me what your implantation cramping felt like? I'm 8dpiui and tonight for about 15 mins, I had some terrible cramping. It felt like I was going to have diarrhea but I didn't. It was so weird. Now I'm just having mild cramps on and off, with kind of the same, I need to pass gas or poop feeling. So I'm thinking that could have been implantation cramping. Has anyone experienced implantation cramping like this? Or know what it could be? Thanks for any input!!