From reading about dressing to your shape I have figured that one is supposed to dress to enhance your curves. I'm 5'8 have a big bum and hate it, am I really supposed to show it off! I just want to wear baggy clothes.

Enhancing curves is fine for those with curves that appeal to most people. Some are quite happy with a big bum. If you aren't, don't wear tight clothes but don't wear baggy ones either. Wear plain (one color) pants or skirts that are of simple fit and that fit just right, with a bit of give even when sitting down.
Oprah did a wonderful show on this years ago. For business attire, she showed several jackets and shirt jackets that were also simple (no pockets, tabs, gathers) that hung straight down to MID BUTT. That's the important part. Don't think that a jacket that goes lower is going to hide more, because it's just going to go side to side as you move and make you look even bigger.
Good luck