You must not have been looking at my quilts ... I do aim for perfection, but I am human.
As for the specific problem your having, yes a picture would help. In general though you said that you are measuring and marking all of your 1/4" seams. Are you measuring them before or after sewing and ironing? Makes a difference. The thread takes up space, and the fabric does as well (when seams are pressed to one side, not so much when seams are pressed open). The smaller the piecing - the more the differences will be in the outcome of the whole block.
I don't know the exact pattern you are using but in general it's easier to press the seams open on star patterns because so many seams meet at one center point. If you are not pressing open, this can throw the whole thing off as well.
So ... show us a photo - front and back of block would be nice, and we'll see if we can help.
And ... if all else fails ... you said that you may be in "over your head". There is NOTHING wrong with putting a quilt away for another day - in this case until you are more confident that you can perform this specific skill, and make your friend a different quilt.
But let's see if we can help you first!!