I am 10 days late. I had a colposcopy on the day I was due for my period Friday May 4th. Never started am now late. Took EPT Saturday first morning urine and it was negative. I have never been this late before. Is it possible it's not showing up on a test?

Its possible that your hcg levels just aren't high enough to register on an hpt yet. However, 10 days is not incredibly late. It is not uncommon to be late, or even entirely miss a cycle now and then. I would wait another week, if nothing, then I would suggest you take a blood test. If its still negative. But you don't get your period by the next expected period date, go to your doctor.