CD 31 no period and lots of EWCM

FM • 34 yo- TTC since Oct. 2012. Endometriosis And 9cm Fibroid excised in Oct. 2015.
My cycles are normally 28-29 days max.  I am now on CD 31 which is completely not normal for me.  This morning I went #2 and when I wiped there was more EWCM then I have ever seen (sorry TMI).  My husband and I used preseed and Mucinex for the first time this month and have been trying for 3+ years.  Could this be my BFP or just an April Fools joke?  I have never been so close 🙏🏻🙏🏻🙏🏻 Only symptoms are sore boobs and a feeling of gas in lower pelvic area.  Took a dollar store test this morning and got a BFN! So confused!  Anyone ever have this happen? Someone please comment!