How can you break a good man's heart? Cheat on him...
You are looking for a reason to leave him?
Loss of love, boredom, need for space. -- choose 1 or all.
Just tell him so to his face -- no bad karma there, you are just being truthful.
Practise, face the mirror, say it again and again, coz practice makes perfect:
I don't love you anymore. (bow)
Take care of yourself. Do what is in your best interest.
Happy Easter, Friend.