Implanted? When can I test?

I’m 8DPO today, yesterday I was having some weird dull pains or cramping and it felt kind of like my uterus was just going to fall out or it was being pulled out of me it was so weird!!! It wasn’t like super painful but that’s the best way I can describe it. I really like to think and hope it’s implantation and I’m pregnant. I’m trying for my rainbow and I’m so anxious to find out. When can I test??? It’s eating me alive. If that was implantation how soon could I get a positive?