One tough reason that might be behind your man avoiding sex with you, is existence of any other girl in his life however, you said he is not cheating on you. If you are sure, then we rule out this option.
There are many reasons that could be behind that problem.
May be your man is under stress (financially, psychologically, might be problems with friends/family..etc).
Try to first ask him if there is anything in life is bothering him or causing him to stress out and let him share it with you to find solutions together.
Try also to ask him, if he does not like something in you, something in your looks, face, body etc. (It might be harsh on you, but you should be open minded and accept any criticizing so that you can work on that area, remember you said you love him so you guys have to be honest with each other)
At the end, you can tell him how sex is important for couples and how it develops any romantic/love relationship to the better. He probably knows all that but you could tell him that again by yourself in a nice and lovely way.
Tell him you want this relationship to continue happily for both of you.
The key, If you love each other, be honest with him and let him be honest with you.
Wishing You All the Best.