/3/ - 3DCG

To add to what others mention, you're missing the crotch piece, which looks kinda like a woman pad. Pic related. Patterns look like flattened UV maps; if what you're doing looks like a planar projection of the worn piece, it won't work.

Tip: if you search "garment name + sewing pattern" in Google Images you'll find some examples of patterns for that piece of clothing. However they are difficult to come by in decent numbers, and the best ones are behind paywalls.