What does it mean to be a load?

If someone tells you that you are a load, it can mean a couple of things. They could mean that you are "heavy" to carry, or that your friendship is a "heavy" thing that is hard to maintain. They're saying that it is a hard job keeping you as a friend.

On the other hand, it could be a coarse slang term, short for "load of sh*t" - this would mean that they think you are lying or acting falsely.