Get some counselling, Chris. I know it a scary thought, esp for a guy but it will help.
As for her behaviour, she seems cold but I suspect she went through her grieving for the relationship long before you actually split. Women tend to 'leave' emotionally well before they move on physically. Which is why its so important for guys to not ignore the signs and her early requests for discussion. Don't sweep stuff under the rug next time.
Be kind to yourself. This too shall pass.
Second thoughts can generally be amended with judicious action; injudicious actions can seldom be recovered with second thoughts.
--Cyteen by C.J.Cherryh