It sounds like you have a boyish figure with narrow hips. Or you might just have ill-fitting pants. A pair with a straight or narrower cut would flatter your frame. It’ll also emphasise your curves and butt.
Also, when shopping for the right pair, avoid the usual range offered by UK brands as the fit of their clothes are usually for bigger, more voluptuous frames. Instead, head to the petite lines.
You could also tailor the pairs you have now. Every brand sews their clothes differently – a size 8 at one shop may be a looser cut than another.