When I first brought it in for winter, it lost a lot of leaves. Then they grew back but now I have the middle stem that has its leaves starting to droop and I am not for sure what's wrong. Does it need fertilizer or what? I don't have it in sun but just light from kitchen where the sun shines in. Would be too cold for it?
Your Hibiscus likely needs a darker location and less watering during this winter dormancy period.
It is normal for the plant to lose leaves and some yellowing of leaves.
Do not fertilize the plant during the dormant period.
Here are some links with more information.