Mine was a single wave of nausea that came and went very quickly very early, but I didn't put two and two together till later (and it may have been coincidence). I like to think the first sign I had was a dream the morning I got my BFP. I was charting my cycle, and at 12dpo I dreamt that I woke up, took my temp and got a 37.7, then POAS and got a BFP. When I woke up, my temp was in fact 37.7 and I did get a BFP! It was quite special.