When should I test?

I (believe?) I'm 9 DPO. I tested yesterday with a $1 cheapie and it was a big negative. I read that 8 DPO is way too early to test? My period is due on 10/16 I believe.

Today I woke up feeling pretty nauseous and I've been experiencing lower abdominal and back cramping pretty much all day. But I don't want to convince myself it's cramping due to implantation or anything because I don't want to get my hopes up. I've also been sitting upright in a chair all day at work, which could cause the cramping in my back right? But I don't think that would cause cramping in my lower abdominal region.

When do you ladies think I should test? I just don't want to get my hopes up :( when did you start experiencing symptoms? How many DPO were you? What symptoms were they? When did you test and get a positive?