You won't like this but the only answer is to eat less of some foods.
I'm just under 8 st but tiny boned and this is the right weight for me- been this size all my life.
However, like you, I find the weight (rolls of fat, let's be honest) go round my waist and nowhere else just as soon as I look at a cake.
You've got to cut back on food. I eat very few carbs. I'm gluten intolerant which helps a bit although I do bake using GF flour etc.
My daily food consists mainly of lean protein, fruit, vegs and a tiny amount of carbs.
I've made small changes, for example, I don't eat sandwiches for lunch, I'll make the filling into a salad. Or have some soup but no bread with it. I have an egg or two every day for breakfast. 1 slice toast. For dinner it's always chicken, fish, lean meat, lentil based veggie dish, and 3-4 veg, then plain greek yoghurt and fruit. And that's it , all day. I don't snack on sweets, or buy cakes or biscuits, or crisps, and as I'm allergic to booze I don't drink that. Once a week we might have a pudding as a treat.
It might sound boring but tbh it's the only thing that works for me.
You also need to watch portion size. If I eat a pudding- like a fruit crumble- I eat it from a ramekin dish. A small portion.