I bet you 10 imaginary dollars, you just need to change your needle. You need to change your needle every project. Yes, you do. FOR FUTURE REFRENCE. Do not, ever, mess, with, the , tension. EVVVERRR. Just get someone else to do it who knows how for sure. the only way tension gets screwed up enough to mess with it is if you throw your machine down the steps. I'm serious. So, change your needle, and re thread your machine. Hope I helped!
Okay, I tend to disagree. You may need to change your needle, but the problem you're describing (because I can't see the pics) doesn't usually correlate with an old needle. As for the "change it every project rule" I don't think that's entirely acurate either. Me sewing for one hour on a light weight purse is quite different from me sewing for 5 hours on a pair of denim pants. I have seen on many places where they say to change it every X-hours, but of course I can't remember which.
And I say, why not mess with the tension? I'm going to assume that we're talking about the top tension and not the bobbin tension. The bobbin tension you probably shouldn't touch unless you know what you're doing. As for the top tension, take note of where it is right now, and then mess away. It's the only way you're going to learn about your machine.
Personally, my best guess is that your machine is threaded incorrectly. Just my two cents.
I've never changed my needle.. i know i need to do that.
But i'm pretty sure I'm threading it right.. it goes through the tension, all the loops and stuff..