Cucurbits such as pumpkins produce very little nectar but quite a bit of pollen, therefore it is not likely that the honey was produced from pumpkin nectar.
As for the crystallization, it is hard to say what nectar source it is from without having it analyzed. But I will say that temperature is a major factor in the speed at which your honey crystallizes, regardless of the nectar source. Yes some honeys crystallize faster than others, but room temperature is subjective. Jars from the same batch will be crystal clear on the main floor of our home, but crystallize if kept in the basement.