This is completely normal, and it will take a long time to recover. You invested 3 1/2 years with this person, it would be a disservice to all that your relationship meant if they could be erased with the blink of an eye.
I recommend being kind to yourself, first of all. Rediscover those things that bring you joy — and do them! You will think you can’t go on, but I promise you — you will. You will be stronger, and even better than before. ❤