Whats wrong with mey lens?

Ok I bought a Canon EF 75-300mm f/4-5.6 III Telephoto Zoom Lens about 4 months ago. When I screwed the filter on the lens, it reached the "tight spot" then got loose again. (the filter isnt going on rite). I figured it was just the filter so kept using the lens with the filter on kinda tight. When one day the filter fell off the lens and broke. So I put on another filter and the same thing happens. It tight but doesnt get tight enough. Can I send this lens to Canon or what should I do. I dont want to have to keep going through filters and its a really inexpensive lens so mayb I shouldnt even put a filter on it

there is a posibility that when you screwed it on the first time, the threads got messed up. by the time you get it fixed or cram filter after filter on it, you'd have bought a better lens. I would not worry about using a filter unless you really need it, since you're having so many problems. just go take some pictures and use your lens cap.