With my last pregnancy, and this one, I knew from the moment I conceived. I could just tell. With my first pregancy we had been "trying" for 2 years, and so I was already ready to test either way. And other than feeling "different" I had no clear indications.
This time, on top of "just knowing" and being COMPLETELY unplanned. I had heartburn from hell, hated my husband (a feeling that has not gone away), and had a sciatic "attack". 6 days after I conceived, I stepped over the baby gate to my daughter's bedroom. and ended up throwing something off (I was at the time recovering from a sprained knee and back), SO as usual, I tried a hot shower to sooth the pain. As I stepped out of the shower, my sciatic nerve was set off. And I laid on the floor for an hour before getting up the nerve to crawl back to my bed.. Two hours later my husband phoned an ambulance, and I landed myself in the ER.
Long story short, I told the on call doctor that I suspected I was pregnant, and he tested, a regular urine test, and it came back negative (Like I had not seen that coming)... Anyway. 10 days later, I tested... Not a single thing I was experienceng was "normal" Though Apart from hating my husband (and that is a bit complicated to begin with) there was no emotional thing that set me off.
Just intuition.