Blanket problem...

I tried looking back through and didn't see this already posted. Sorry, if its a repeat though.

I am crocheting a blanket/afghan and I am having some problems. The pattern is very easy ch75 then 60 rows of sc. But instead of using 1 strand of yarn you use 2. The hook required is 15mm and the yarn required is a bulk 6weight. I am using both of these. My problem is even though the blanket is soft because the yarn is soft its very....stiff. like its not drapey or flexible at all. its seems like it would be awkward to use as an actual throw.

I held the yard loosely but maybe not loose enough? Maybe I should use an even larger hook?... I can't figure it out. I'm only about half way done so its no problem to take it out and start over if anybody has the solution.

Thanks! Its supposed to be a bulky blanket but i still feel like it should be flexible and floppy like an actual throw.