Feeling so discouraged!

Bonnie
Back on 12/29 I found out I was miscarrying at 11 weeks. We tried for 4 years prior so it crushes us. I had natural miscarriage, bled for 8 days. And on Jan 7 they did a blood test and my hcg was down to 18. I was told we could start trying right away. I'm now on cd 26. Weve bd'ed everyother day. I've tested with ovulation tests since cd 15 every day and have gotten the same result. I was told to look for ovulation right away since my levels dropped so much. what's the likely hood I missed my window? Or coukd these test be indicating hcg for my past or new pregnancy?