To test or not to test?

Ok so AF was due on Thursday according to my Glow log, however this is for a 'normal' cycle. My average cycle length is 40 days so this is actually day 38. I'm stuck between being desperate to test as I'm 5 days late but also pretty sure I'm going to be disappointed because my cycle is longer! What is most annoying is that my cycle has got longer in the last 8 months. My periods have become less regular! My cycle is never the same length every month so I'm really not sure what to do! I don't want to be disappointed but I also don't want to continue like normal when I have a big social occasion at the weekend! Opinions needed ladies! Thanks