From what I've learnt here the HCG doesn't start to go up until after implantation and I've heard this happend between 5-8dpo but there are lots of variations. I would wait another day or two. I had an implantation dip at 9dpo adn got a very very faint pos at 11dpo. Didn't get a really strong pos until 15-17dpo. Fingers crossed for you.