Seeing as I start vomiting from about 10dpo, and don't stop until bubba is born, I kind of assume all symptoms aren't psychosomatic!
Things like implantation bleeding, cramping, backache, nausea etc can start quite early. I don't think you can get symptoms before implantation, so anything before about 8dpo is probably just normal pmt symptoms taken out of context, or miscalculated ovulation.
I've given up symptom spotting, every month, my damn body throws something new at me, and it doesn't mean anything, and hasn't for 13 months!