Why do my stitches look weird?

Can someone please help me figure this out? I got a singer heavy duty for Christmas and it was working great until it wasn’t. I was making garland for my friends and then went to change the stitch to a zig zag for style reasons and my machine wouldn’t do the zig zag stitch. I switched it back to the straight and then after that my fabric kept getting pulled into the bobbin case multiple times. Yes I did trouble shoot it and looked into why it was happening. Eventually I just gave up and packed it because I had to drive back to my college town. Got it out today to make luggage tags and now my stitches look all weird. I threaded the machine correctly and my tension is on 4. Can someone please help me fix this? I don’t know what to do and I just want to sew. I have never run into this issue before and I don’t know what’s going on!