Day 33.... still no period

I am normally between 28-30 day cycles and I'm currently 3 days late. I feel really stupid thinking I'm pregnant because I have unexplained infertility and we are just about to go see a professional but I am beginning to feel that this is it. I've been having lower back pain and acid reflux which I never ever have had before now, I had to google what it was. A year ago I promised myself I would stop testing for pregnancy until it was so clear I was pregnant that I knew it was going to be positive. After a year TTC I was exhausted with the constant cycling and testing so I ditched all tests completely. 

I'm tempted to do a pregnancy test but I'll kick myself if I've been sucked back into spending money on something that is clearly not happening! I'll also feel foolish. For a while I thought it was just a cruel joke to have to test when you are getting negatives all the time. 

Thoughts?!