When should I go in for a blood test?

Mommy to Kai

I'm planning on just skipping the HPTS and going to blood since it's just a walk in clinic here on base...

My fertile window started on the 3rd I was almost 100% positive I Od on the 4th from cramping and ewcm but then again last night I was cramping with ewcm. All opks have been NEGATIVE :, (

Period is due in 11 days. When would you go in for a test?