How long have you been keeping track of CM in your cycles? If you have trouble finding the EWCM (in your panties) that will indicate fertility, you may have to check CM at the source.
This might not be a bad idea to do anyway for a couple reasons.
1. If you are checking for EWCM at the 'exit' it takes some time for the CM to migrate down from the cervix to your panties and along the way it might become less EW if the extra fluid is absorbed by your vagina. And if you have a short fertility window you might be timing intercourse a little 'off'.
2. While you're 'up there' you can make a quick note of a secondary fertility indicator - Cervical Position. This cross check is helpful in helping to determine fertile window, but remember it should NEVER be used as a primary indicator.
Good luck to you!
