Positive OPK - normal?

Is it normal to have a couple of days EWCM and be testing negative on an OPK and then no EWCM and test positive for two days? This happened on my last cycle. I had EWCM yesterday and today and yesterday’s OPK was negative. I am guessing today’s will be too and possibly tomorrow’s and then positive on Thursday. Or am I just missing the surge on the days when there is CM?