Hi. recently i've been getting frequent pains in my arms,shoulders, knees and thighs. the pain is kind of dull and achy. and i get bad headaches. why?

Hard to say: The symptoms you describe are very varied and could mean a lot of different things. This could be something as simple as an oncoming cold or flu. Muscle and joint pains in multiple areas usually mean a systemic illness. I would recommend a visit to your doctor to be evaluated as so many possibilities exist for the symptoms you have described.