oh, i wish i could answer your question. 20 years is a LONG time to have an intimate relationship with someone. you probably know when he is going to take his next breath. i think it just takes a long time to grieve that loss.
we can get so stuck in the "could have been" stuff, ya know?
i think an important relationship that ends rather abruptly, leaves a bigger scar to heal. it almost sounds as though one morning you woke up and he was gone.
i know you are sad. but are you doing anything good for yourself yet?