*TMI* strange AF- some insight please?

[Calluna]

Normally I have my period for about 8 days and is light to medium flow, red blood, then light flow, brown blood for the last 2 or 3 days. The last one was heavy flow, dark red blood right from the start and lasted about 4- 5 days then just stopped as suddenly as it started.
I often get nasty cramps, about 2 out of 3 periods will be preceded by very painful cramps that start the day before or on the day I get it and last 1 or 2 days at most. This time I had no cramping until 2 days after it finished. Rather than the almost constant pain I usually get, they have been on and off in varying degree's of pain for the last 3 days.
I thought for sure I was up for the second wave but it never showed.
I've also had quite a lot of CM the last 2 days. Enough to have to change liners every 2-3 hours when normally I'd only use one a day! It's clearish/ white and the consistancy of snot.

There is no chance I'm pregnant as we haven't DTD in about 4 months.

Can anyone tell me what's going on or at least give me some idea of what might be causing it?

Thanks