CM: a little long, but need advice.

So, I have been ttc baby #2 for 2 months now. Af is suppose to come the 28th, but today I have been having a lot of eggwhite looking cm. I took a pregnancy test, but it reads bfn. I've had a lot of nausea and fatigue this past week, and I was just wondering if I maybe ovulated late or is my body just getting ready for af? (FYI: I have been off of the nexplanon for 2 months, and have only had one, five day period, and I also took did the OPK this month and didnt have a "high" or "peak" reading during my fertile window so i stopped.)