25 & TTC Immediately after Miscarriage 3.5 wks ago

Ladies, I've finally been cleared and been given the okay to start "TTC" again, now that my HCG level is 3. I had already started "TTC", but I wasn't tracking my "CM" carefully. I started taking the OPKs and they were all negative. I fear that I might have missed my peak days, but the doctor spooked me saying it could take 12 weeks to get my cycle, back. I'm trying to see what is the proper way to determine when my cycle started and how to track my ovulation. I'm extremely anxious to try again and I pray to God I become immediately pregnant because I really wanted my baby and I have been TTC for like 5/6 years. Please comment. I welcome all feedback!