TTC again BUT...

I had a miscarriage 2 weeks ago and I want to TTC again so the DR gave me the go ahead and I think i should O any day now because it's been 15 days since  my miscarriage which my DR says I should count as day one well the down fall is I don't know when to try my husand and I can only try once in my fertile window and I can't rely on OPKs because I'm still testing positive for HCG so the OPK is a false positive and I don't feel like I've really gotten the normal EWCM that I normally have when TTC lie it was sticky and I though oh it's about to be EWCM in a day or two but it just went away now I just don't know what to do. Has anyone else dealt with this how did you know when to try