How should I start telling him how I feel?

Sounds like you are asking how to write a Dear John letter. If you do not know what that is, it was a typical letter that boys/men that were serving in the armed services would get from home telling him they were calling it quits, leaving him, etc. Whether it was a marriage that fell apart or a torrid love affair that died, or a giant bone-crushing crush that faded, the recipient of the the "Dear John" letter always died an agonizing death of at least the heart.and in many cases for real, as during their next battle engagement would risk it all to die since there was nothing to go home to anymore. Despair is the order of the day when it comes to a Dear John situation. Both sides feel it. It is just how each side reacts that makes all the difference.

In your post, you wrote: ".I no longer like him.", but just 5 more sentences later, you say, ".I still love him."

So, which is it? You need to answer that truthfully to yourself before you run the risk of breaking this guy's heart into a million pieces. Whatever the answer is, please stick with it. Good luck.