6 days late, no sign of AF but hesitant to test

So... I'm late...by almost a week, which isn't normal for me, I have hypothyroidism but my period is normally as regular as clock work. But nothing this cycle. The reason I'm hesitant to test is that my OBGYN told me I have a thickened uterine lining and embryo attachment is impossible for me almost a year ago, after TTC for 9 months. I am freaking out like you won't believe. Somehow I just think it's stress related, but need to take a test soon as I work in a chemical lab and only got back to work two days ago after the holidays. Luckily no work has been done in the lab yet. I'm so nervous. Someone talk sense into me. I've had too many negatives over the last two years.