Accused of cheating

He thinks I'm cheating and I never have and never will cheat on anyone I believe it's wrong and anyone who does it should never receive any form of happiness until the end of their days and it honestly hurt me so bad when he accuses me because I'm beyond in love with him he is everything to me I wouldn't want to live without him and when I asked why he thought I was cheating he said that when we made love last night I felt looser and that he just has a gut feeling and it hurts me so bad because I'm faithful and all I want is to marry him I tell him this and ask him to trust me and he just says idk what should I do I suffer from depression and anxiety and all I want is for him to trust me I mean we have been together for 3 years I love him and only him