The discharge does come with pregnancy but with me it does around my period too.
I was also worrying about the exact same thing. I am now 3 or 4 days late. I tested at 1 day late and got BFN. I have nausea in the evenings and through the night, and since yesterday, slightly tender nipples.
I have stopped worrying about the CM and am now very optimistic. I am going to try not to test this week though. and if my period still doesn't come next weekend I will get a blood test.
(well I say that now, but chances are I will cave in this week some time)