Have you ever felt lonely in your relationships?
I use to feel lonely which lasted for a year in my nearly 6 year relationship until it ended few months ago when I realized that the real problem was in me.
As CryoDream suggested...you should talk about it even if it makes you very uncomfortable. If you don't want to discuss face to face, write on a paper telling him how lonely you feel, how sad it makes you, etc. but don't speak/write it like a complaint...write more like a confession. and give it to him.
But don't try to consider moving on soon...during the rough times the relationship looks weaken and we often feel very lonely, but that doesn't mean it should break/end there.
Unlike many relationships yours isn't about cheating or abusing etc. It's just misunderstanding, fights always arise with misunderstanding and lack of trust/confidence in one another. Try to understand each other everything will resolve.