What should I believe?

Ok so I’ve been seeing this guy for about 6 months. I told him how most of my relationships barely last more than 3 months. He said the reason behind it is because I am a “casual” thing. He also said that he doesn’t see me that way and that he would’ve already had stopped seeing me if he saw me that way. I don’t believe it and now I don’t know what steps to take now since he said that.
What should I believe?
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