Ex FA bf moved on quickly.

i'm so sorry, i know you are in a lot of pain.
the pain will not be reduced by telling him how you feel.
it will be exacerbated by humiliation and whatever response or non-response you receive from a man who is not able to meet your needs and who has moved on to act out his dysfunctions and disappoint someone else.  That's the real deal- he just found another person to use and mistreat.  Letting him do that is your first step in changing your own patterns, which is what is really most important to you, you're just triggered.

yoi know you can't continue down the same road with the same people, you're trying to take another path now with new people.  This is an excruciating first step but it is a step toward letting go.... don't tell him, tell the people who can help you get through it, as horrible as it is.  He can't help you, he can make it worse for you. 

i'm very sorry. 
this makes me think of that post i wrote about letting go of an attachment that causes deep harm, i can't remember what thread it was on- but this would be a good time to read that .  and keep posting here instead of reaching out to him and opening yourself up to that cycle that has proven itself to be painful, time after time.