Why does he get mad if I don't take his help?

We are in this relationship for a little more than half of a year. We don't live together, split all the time, never give each other gifts - in short there has never been anything financial. He has a good job, I'm still a full-time student. Recently I've got a university project that needs some help (non-financial). I was talking about it with him and he said he can totally help me, it's easy for him. But, I feel uncomfortable to take his help since it would give birth to a terrible gratitude. Besides, even though it's hard for me to do this work, troubling him with it just doesn't feel right to me, this project is my problem, not his. So I denied and he got mad.

Did I do it wrong? How to handle this situation?

Why does he get mad if I don't take his help?
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