Loose lower stitches?

Please please help me!

I recently bought a brand new Empisal Celebrity 550 Sewing machine, I've used it maybe 4 times up to now. Yesterday I was sewing with it and everything was working perfectly, today, when I got home, I plugged in the sewing machine and started sewing, just to see that the bottom stitch is completely loose. It's making these loose loops instead of stitches? I didn't change a knob or anything from working with it yesterday to today, so I don't understand how it all of a sudden doesn't work? I've read some forums where people say it's the tension on the bobbin that causes that, but I haven't touched it. And if it is the bobbin, how do I adjust it? There is no knob or lever or anything for my bobbin (Well not that I know of). If it is the bobbin, where do I change it's settings?

If someone knows how to fix this, could they please explain to me in a very dummies way how to do it? I'm still completely new with sewing.

Please help me, I'm on a very tight deadline for a university project and I don't have a clue what to do?