Start with a six-letter word. Tack on a contraction and it looks for answers on its own, or tack on a conjuction and it will investigate only what is right in front of it. The former is alive, while the latter is inanimate. What is the six-letter word?
Start with a conjunction. Add a letter to find it underground. Add a letter when you drop that on your foot. Add a letter and get some aspirin there. Drop a letter and you actually hurt yourself more than you thought. Drop another letter and they have to remove this. Drop another and end with a preposition. Combine and unscramble the start and the end to find the cause of your problem.