Please don't be ashamed. when I bought my latest machine about 9 years ago, the dealer never told me one thing about cleaning out under the bobbin case. After I moved here and began sewing so much more, it began to make a clunky sound so I took it here to be serviced. That is when they told me that it was crammed full of lint and showed me how to clean it out. I can tell by the sound now when it needs it but I do it at least every 3rd or 4th bobbin change. I still get it serviced every 18 months or so just for good measure but just cleaning it out helps a bunch. Like I said, someone just needed to tell you.