I had sex the 7th and 8th due to ovulate the 9th I have 11 days til expected period but I am having severe cramps any idea what would cause this?

Implantation? Possibly, you could have a pregnancy implanting on the endometrial wall, causing some inflammation leading to cramping. Usually, though, this would not be severe. I'm not an ob/gyn, and i would recommend seeing one if this problem worsens. Also, crampy abdominal pain could be from a GI source and unrelated to this process. I'd be interested to see what my ob/gyn colleagues would say about this.