Well before you do anything, be sure that you actually want to break up with him, i think the best way to do this is to sit down with him, tell him that you're thinking about it, see how he feels, then perhaps talk about it together. You said he doesn't seem interested in you anymore, well talk to him first and see if this is actually the case.
Communication is the key, you might still be able to stay friends if you break up.
Don't say to him "I'm breaking up with you" right out of the blue, that's an old cliche' way of doing it and it mostly always ends in tears.
The rest should fall into place, just be sure before you do anything.
PM me if you need any more help on anything.
Good Luck
ImSoHappy
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May the wind always be on your back and the sun upon
your face and may the winds of destiny carry you
aloft to dance with the stars.