I think babydolls are cute and sexy, not frumpy, you probably would look adorable in one to your boyfriend since he is obviously attracted to you.
But, since you are pear shaped, I don't think it is the most flattering of shapes. They look cutest on girls with small hips, I think, flowing straight downwards and drawing attention to their chests. On someone with bigger hips, they would go outwards from the chest down having the opposite effect and also hiding the waist/making it seem like you just go straight outwards which you don't.
I think something like this would look knock-out sexy on you:
http://www.lasenza.co.uk/babydolls/babydolls/Level3.aspx?d=22&collection=9&style=704190&product=030014506&img=AW311_39I could be wrong, you'd have to try it on (although your opinion could be clouded by your lack of confidence and you could think it looks really bad when it doesn't - so maybe, if you have anyone you are close enough to, you could try it and ask a girlfriend for an opinion?).
I don't think it would matter if you had 'lumps and bumps' that would stick out in places perhaps, for a start he knows what you look like and loves you. But also, it's a very visually striking thing to wear - with bold lines, like the suspender straps against your skin, especially at the back with the diagonal lines of the underwear too. It creates an exciting overall image and shape that draws away from anything that might be sticking out. I think it would make the most of your hips.
You could wear a suspender with a corset or basque though, showing your waist, making your hips look yummy with the straps on them and also keeping any wobbly bits in - if you'd feel more comfortable.
This is all just my opinion though, I could be wrong.