Married for only 3 1/2 yrs, he don't want to have sex

He is only 43 yrs old and we have only been married for 3 1/2 yrs. for the 2 1/2 yrs i have only been getting sex about 2 times a year. He is a healthy man, but when I mention it to him, it is always he is to tired, or I don't come to bed when he does ( he works from midnight on). But i have went to bed serveral times when he does, no luck. Last night when I went to be, he put a pillow between us. I just don't understand at all. I have tried so many things to entice him, but get no where. I only get a peck on the lips now days. He is a great husband on all other areas, it is just this one area that needs fixed.