Welcome and congratulations with your first quilt.
Keeping 1/2 inch seams is hard to control. I suggest you keep your seams to 1/4 inch and use a 1/4 inch foot. If you don't have one, select a foot and keep the fabric aligned with the edge of the foot for all the seams, but make sure the seams are at least 1/4 inch so the quilt can hold strong.
Maria