U ramble away !
I would think that it's a combination. Peri-menopaause throws up weird and not so wonderful health issues. Also, U may still be in a fight/flight/high alert mentality so be kind to yourself.
R U still having to engage with him? That situation would keep you on alert.
Working in your work situation may well compound the past issues with your ex.. How much support do you have in your work place? Would you be able to take a different role for 6 months to ease how you are feeling.
I think 1 has to grieve for the loss of a friendship or relationship. So anger and irritability probably go with that.
Is there a talking opportunity within the workplace or perhaps think about some counselling where U can vent. It did me a World of good ;-).