Lack of sex

My partner and I have been together 2 years. We use to have sex a couple times a week. We are lucky now to have it once a month. I've brought it up to him and he said just masturbate but I said it's not the same, sex has that connection between us that masturbating can't have.

He says his tired and doesn't have time, it just makes me think he isn't attracted to me anymore.