Mid cycle bleeding two months in a row, not pregnant.. Concerned.

Hi ladies, hoping maybe someone might be able to shed some light or ease my mind a little before I am able to get in to see my GP on Tuesday..

Last month, 6 days after the last day of my period, I had brown spotting. I've NEVER had mid cycle spotting before. It only lasted that day and went away so I thought maybe one odd month, no biggy. This month, on day 5 after my period finished I had the tiniest bit of brown spotting. On day 6 after the last day of my period, the brown spotting got a bit more noticeable, now today on day 7 after my period ending, it's noticeable brown spotting with flecks of fresh red blood too. It's increasing this month.

What is that?! I know I shouldn't have googled but of course I did and my other symptoms fit either Underactive Thyroid or Cancerous happenings. I have been very slack with having a Pap Smear and will be booking that Tuesday now let me assure you..

Any others had this happen and gotten any answers? My periods are irregular, ranging from between 27 day cycles to 40 day cycles, the past 3 cycles have been around the 28-32 day mark though. I am not currently ovulating, likely I will in the next few days thought perhaps.. I've never bled before ovulation before though?! Absolutely not pregnant at all, that is definitely not the cause.

Any ideas, experience or advice?