Good morning Cheri! Please don't give up. Is there someone you can get together with to perhaps watch what you are doing? Sometimes, it's the littlest thing that we don't see ourselves. I know it can be frustrating after we've spent all our time being so careful and then not have our pieces match up. I've been at this for about 17 years and I still have troubles sometimes with what you are talking about.
I do remember one time that someone said when you are cutting, those lines on our rules can be pretty 'thick'. So, they make sure their fabric is a thread to the right or to the left of that line. I don't know, I wish I could come over and watch ya!! I watch my sister and she swears that she is sewing a straight line, but when I watch her, her fabric is not lined up with the point in the presser foot to give her an accurate 1/4" seam. It took her awhile to tell me she was having a hard time seeing where she was going cause her lighting was good - haha!
How about a class? I get so much information from those - even from other students in the class.
I wish I could help cause I can feel your frustration.
I can give you some HUGS though!!!!!!

Hugs,