I had the methacholine challenge test and it triggered bronchospasm on the lowest dose. What does this mean? Should I be on bronchodialators? I'm 27.

Probably. It means you may have reactive airways disease. There are many inhaled drugs that can treat this, and published guidelines. Talk with your doctor about any further testing and follow his/her advice.
Yes, if bronchospasm. Nick-there are many different types of inhalers used to treat bronchospasm, one class specifically reduces 'swelling" of airways, the other two classes act directly on airway smooth muscle. If methacholine is a pronounced trigger, you may benefit most from a drug called ipratroprium bromide-this opposes the effect of choline.