as im young i am quite fit but i have a bit of a flabby stomach i do sit ups but they dont work wat can i do is there anything for like my lower abs because thats the problem?
You can do as many sit ups as you like, it will not reduce the fat around your stomach. It will just strengthen the underlying abdominal muscles.
I presume you are female, if so, then as women, we tend to hold our fat stores around the lower stomach, hips and thighs. The only way to improve is to ensure your diet does not contain too much saturated fat or too much sugar. You might find doing light weights may help to burn fat stores, but often, it's just genetic.