Trust in relationships

My husband is in the military and I don't live with him atm. But his nature is very untrusting of other people. He's always trusted me more than anyone else but from the very beginning he always asks if I'm being loyal. I've never cheated on him or anyone for that matter. I take relationships very seriously and he knows I'm an honest and loyal person. I trust him and never worry about his loyalty, so when he says he needs reassurance every day, I fail to do so because that's not on my mind. When he asks so frequently even when he knows everyone I work with and what I do all day, it makes me feel like he's expecting it and it hurts me that he can't trust me as much as he should. Am I overreacting? Is this no big deal like he says?