Sarah,

I'm not too sure but my thoughts are as follows.....

I agree with BW that decongestants could dry up cm. You could also get this from being dehydrated if you're sick (ie. from fevers, runny nose etc). So that could explain a lack of ewcm. Sure illness can definitely affect O. I would expect your body would O when the illness/stress is gone so that would mean a late O. If you don't O then I'm not sure what the go with AF is.... I have super irregular cycles so often I have to wait 6 weeks to O but I know I won't get AF until that happens. If you don't O this cycle then maybe you'll just skip the AF too and won't get AF until after you next O. Sorry I couldn't be of more help.

Get well soon