Is he losing interest in me

I am in a relationship with a fellow for nearly 3 years and I feel that his feelings are not all there anymore. How do I tell that he feels for me as I feel for him? Just the other night after not being together for 5 days intimately. See each other every day but do not live together. Nothing happened. He lost his erection and I felt like crap! He assures me that it was because he had a few drinks of alcohol. True or not? I felt like just picking up and going home but he won't allow it. He tries to reassure me that it is not me and I am desirable to him. I am overweight and I feel that is the major problem. When we met I am the weight I am today. How can someone that is horny lose all desire instantly. Guys help out here and gals if you are reading this and this has happened to you how do you cope with it. I feel very strongly that intimacy is the #1 thing in a relationship and right now I feel I am losing the man I love!. This has happened a few times and the same explanation and I feel that is a copout. Am I being paranoid? He is a widower and still has pictures of his loving departed wife still in the living room and his bedroom and some of her personal belongings still remain around the house.