I say that "getting up" is something that "I hate. The covers I have on my bed are heavy." The covers, "covers," are the things that you put over you to keep you warm.
Usually, the covers include a blanket, sometimes a comforter and usually, what we would call the top sheet or flat sheet.
A comforter, "comforter," is a very thick blanket--a very heavy blanket.
A blanket, "blanket," is something that you put over you when you are sleeping to keep you warm.
Blanket is a general term; a comforter is a kind of blanket--a heavy blanket.
The opposite of a comforter would be a light blanket.
A light, "light," blanket would be the opposite, and that is a blanket that will keep you warm, but if it gets very cold, it might not keep you warm--it might not be sufficient.