Why is he accusing me like that?

Ever since my boyfriend and I started dating, we spent a lot of time together, he always invites me to come to his house

The thing is that for Valentine's Day, I wanted to make an extra handmade gift for him

So I needed time to do this, I wanted to keep it secret so I told him I needed a day to do "something"

My mistake, because as soon I said that, he began to interrogate me, asking what was what I needed to do and even told me jokingly "Usually, girls asks for a day like this to cheat on their partners"

This is my first relationship ever, never have involved with anyone else before

I just wanted to do a nice and thoughtful gift to show how much I love him...

Why is he accusing me like that?
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