Hiya
I am on my second cycle of clomid which I take CD2-5. I use the CBFM each month, and last month just had 16 days with high readings. From what I understand by the instruction booklet, the problem is that the estrogen levels can increase so much that it can block out the LH surge, which makes detecting ovulation much more difficult.
The hospital didn't want to do scans for me, as I am on such a low dosage mainly to give my ovaries a boost, and there is no risk of OHSS (or whatever its called). They told me that my ovulation date would be pretty much unaffected. To be on the safe side, we make sure we BD as much as possible from the day I stop the clomid until CD17 (as pre-clomid I ovulated on CD11 at the latest).
Hope that makes sense, and helps a bit.
Good luck on your tabs - let us know how you get on.
xx