when to test..?

some back story.. I had a MC on June 10 and did not officially have a period. I was using opk to find out my most fertile days so I could try again, I ovulated the past 2 days.. I am about 75% sure it took because I already feel my usual pregnancy symptoms but I want to know when and how are the best ways to test.. I have a requisition for blood rests from my dr in case I get pregnant.. should I just go through with that right away or do I have to wait for my HCG levels to increase?