i've read it takes about two years, but after 6 months things can get a little better. i'm glad you left for your son's benefit. i would have had to do the same if i'd had a child.
yeah it's losing someone you really cared about and felt right with, but sometimes you have to do the hard stuff and you're doing the best thing for your son, and later you amy realize it was the best for you.
it really hurts, the sorrow, loneliness, loss of the life you had, but you'll get through it. you can go on and build a new life, and it will be better than what you had.