Thanks so much for your thoughts and help!

It's only a little cheapie machine. I've had it for almost 3 years, its had minimal use and never been serviced... how much does a service generally cost? I've never changed the needle- maybe I should try that? I am sewing PUL (and filling it with holes!!!)... but I'm repairing nappy covers and have done a few already with no problems so surely the fabric isn't an issue? How do I know what type of needle I need?