"I'm not looking for anything serious"

I understand how people can get carried away during midnight conversations lasting until 6 am, but I felt in a way deceived when he only now expressed how he wasn't looking for anything serious, whilst we've been going out for a month.

I suppose I built up a lot of it in my head and I regret fighting with him about it. I haven't spoken to him since the argument. It's more or less over, so point being is I'm hung up and I don't know how to get over it.