When you're alone, you must feel cold inside.

当你孤单的时候，你的内心一定觉得很冷。

Do you feel cold?; Are you feeling cold?

你冷不冷？

I feel cold and shivery.

我觉得冷并且发抖。

I feel cold. I have a headache.

我觉得有点冷。我头疼。

Turn the heater on if you feel cold!

若是觉得冷就把暖气打开！