How do you tell partner you're not happy?

Background first...my partner is difficult. We have had up and downs but we have been going strong for about 3 years now. He doesn't like emotions or feelings and doesn't like talking about them. I've tried to accept his nature and learn to adapt but I am having a hard time.

My emotions go unnoticed.

My requests for affection are ignored.

I put every ounce of effort I have into him and it's rarely reciprocated.

We only have sex when he wants it.

I'm not happy. How can I tell him I am not happy without it leading to a break up? What can I say to ignite a flame under his butt and start to please me?

The last time I told him " I don't think I am happy anymore." ...he immediately asked me if I was seeing someone else.

I have gotten the responses " if you're not happy then leave, I'm not changing , ect".

Someone give me some ideas