How long have you been using the cbfm?
Im asking as i never had eny trouble like this until i started using it last month after my mc in feb..and it started asking me as usual on cd 9 (as i have 31-32 day cycles) but i had highs as of cd 13 until i finally peaked on cd 18.
Its not normal for me but its possibly due to the mc... I know some people have troubles although if you have bang on cycles and of normal length it should still work....hmmm. have you tried the cbfm website?
http://www.clearblue.info/uk/FAQSFAM.cfm
Hope you find some answers chicken,sorry ive no good advice, all the best though, xxx