Hello ButtQueen!
Sorry to hear of your suffering!
Hope you find relief soon!
Just wanted to reassure you that you are not the only one as I too have this extra constipation problem in the lead up to a period & I so totally feel for you! Then as soon as period starts it does a 180 & the very soft frequent stools brought on by the severe cramping & bloating starts.
My CRS said that this is a completely normal pattern for women yet most women whom don't have gynaecological probs nor issues with their bowels don't even notice the the changes in bowel habbit but then there are the one's like us that do have butt & or gynae probs & it escalates into being another issue to balance.
I keep track of my monthly cycle & physically are very aware of the changes to my body throughout my cycle & start to counteract the event of constipation by either taking extra Movicol if I feel that it's going to be required or include foods that I know are triggers for my IBS to try & create a counter balance.
Maybe another option for you if you feel that a few months without a period would benefit the healing of your fissure is to perhaps look at some birth control options where you can posibly go without a period for a couple of months.
Good luck with it hun & healing vibes to you! :)