Most Helpful Guy
My wife was married to a man for five years before me. He died. We have been together for over a decade now, married for over six years. She still thinks about him sometimes.
I still think about all of my exes now and again. There is always the thought of what might have been. Hell, I still think about the crushes I have had throughout my life and wonder what might have been.
Is it unhealthy? Only if you let it negatively affect your current relationship.
Will it go away? Not completely, but it may fade with time.
My advice, give yourself more time to heal before going into your next relationship. You are young yet and have plenty of time to find the right relationship for you. Going into new relationships too soon is not healthy.