I feel cliche at this very moment

Yesterday I found glitter on my fiance's penis. We have been together 4 years, survived military deployments, etc and not once has there been any suspicion of cheating with either of us. We have nothing in our home that has glitter in/on it because when we first met, he told me he hated glitter because of its tendency to get stuck on your body, clothes, etc. I have purposely avoided it for that reason.

Our relationship is amazing and so is our sex life. I have never had any reason to doubt his fidelity, but now I am so confused. When I brought it up to him, I was calm and trying so hard not to accuse him bc I understand how hostile those kinds of conversations can be. He tells me he doesn't know how it got there. Tried to tell me it was me, but I know for a fact it wasn't. And he told me that while at his friend's house, there was no way it could have gotten in there accidentally. I don't understand why he would add that when I felt I needed some assurance.

I know that all I can do is trust him or leave him. I haven't spoken to him since yesterday because he told me my accusations were "bullsh*t" and he started yelling at me for hurting him. Would someone with nothing to hide treat someone they love like this?

Is it normal for me to feel this way? Am I being blind & naive or am I making this out to be worse than it is? I don't have many female friends so I don't know if this is normal female behavior. Am I doing something wrong that is making him angry with me? I have taken his feelings in consideration without compromising my own. Other than that, I don't know what I should be doing.