Implantation cramping??? what did yours feel like? (2ww)?

Last fri 9/10 I had really intense cramping.. thought AF was arriving early... cramping lasted from about mid day til late Fri night... I got off work and just wanted to lay down.. I was feeling really displaced and spacey... decided to text my sister to see if she had any extra tampons, (didnt wanna stop by the store) and accidental sent it to the hubby..(lol).. so we went to the store anyway and I left my bag at the register.... got home and still felt really crabby.. no energy, just wanted to lay in the bed and cover up..the cramps felt so much like AF.. finally they stopped and have only been very min. since.. AF not due until 9/15.. could this have been implantation? how long does it last? when can i test? thanks in advance for your help!!!