Hi and welcome
You are using my favorite needle size and yarn thickness but if the pattern is using 4 ply then it usually uses smaller needles.
If you followed the pattern as stated you will end up with a garment much larger than what you require. If you double the needle size and yarn your garment will be almost 4 times the size. I know this because this t rex was small but I wanted it big.
Do a large swatch with the pattern eg 40 X 40 stitches and then compare that with the tension recommendation in the pattern and try to use even tension and I apologise if you know but that is how tight you make each stitch. When you measure make sure that the swatch lies flat and is not stretched.
So absolutely no problem if your swatch tells you that it will be too big unless there is a pattern that needs a certain number of stitches but that can be solved too.
pm me if you want because working out sizing is just simple maths