Almost positive opk then completely negative

I miscarried in Feb and since then I haven't even gotten a second line on my OPKs until yesterday morning at 10am. I got an almost positive. I took one with fmu (I've read online to use fmu and some say don't and I'm so confused) and barely got a line again. Did I miss the surge or am I just not ovulating yet? Do I keep testing? Someone please help me understand. Google is not helpful. I'm using clinical guard opk.