I am sorry to hear of the untimely death of your BF. Please accept my deepest sympathy. I would wait to see what the results of the autospy show before you go any further. I know it is hard to believe a person can just go that quickly but if he had heart disease he was not aware of the autopsy will show that.
You did not identify which medications he was on. His pain pattern and location do fit a heart attack but as always it may have been something else.
Take care and gentle hugs to you,