Need some help!!!

So currently I'm 7 dpo. I had a successful ovulation. I'm on second month of clomid this was just an extra helper I guess you could say from my doctor. Here is the kicker, I know around 5 to 7 dpo is when implantation happens. It's very rare that it can happen around day 4 to 5. I refuse to buy hcg tests because all I do is waste them and non stop test. But i decided today to take an ovulation test and it was as negative as negative could be. Like the second line wasn't even visible. I have been doing some reading and people say opks can act like a pregnant test. Am I out this month. I really thought we did it this month. I was so positive that I was going to get pregnant but the close we get to my aunt flow I'm feeling that same loss I feel every month. Do opks pick up 7dpo? Or am I not being patient??? Helpful answers please. My husband and I have been trying a year. We did get pregnant and lost our baby at 7 weeks and have been out of luck since.