Waiting for colposcopy appointment

Please help I desperately need some advice. I went for a check at the docs as I had been experiencing unusual periods that were slowly becoming black and tar like. My last period was completely black. I had been suffering from spotting around mid month for about 4 months but that had stopped. Had my hormone levels checked. All ok so put me on Yasmin for three months to see if that sorted it. I'm off Yasmin now and still black horrible period, no smell really just irony. Sorry for the detail. Anyway went to gp who checked my cervix. Says I have a dark area on my cervix and has never heard of black periods before. Has put and urgent request for a colposcopy and I am waiting. I have no other symptoms other than a little cramping now at mid cycle. I am 35 years old and so worried. doc mention cancer and looked mortified.