Hi deema,
I am sorry you are having problems.
I have the same machine you do. So do lots of others on the board so hopefully our collective minds can get yours back on track.
If it were happening on my machine I would:
Take the top thread off, take the bobbin tread out. Set them to the side.
Take the bobbin case out, set it aside.
Remove that grey plastic cover that covers the bobbin case. I can go get my manual if I need to know what it is called.
Remove the throat plate so you can also get to the feed dogs.
When you have everything off that is supposed to come off, get a thin handled,long handled brush. The ones that come with water colors are like this and work well.
Very gently swish the brush around inside the machine where you can not see. Gently, because you don't want to break or loosen any of the springs. Get all the lint out you can. Then use the brush in your bobbin race, turning the wheel slowly as you do.
After you finish with the bobbin race clean the feed dogs, again turning the wheel by hand to get to any small lint your eyes might not be picking up on.
Trust me on this one, I do it on a regular basis. Take your machine oil, put a dab on a qtip or your finger. Rub the oil on the needle holder rod. Turn the hand wheel so the rod goes into the machine. Do it a time or two so the needle holder rod has lubricated inside the part it goes into. Then put just an itsy bit (not even a drop) into your bobbin race, right in the center. You can use the same qtip or your finger.
Now, put all the parts and pieces back in taking care to line your bobbin case where it is supposed to be in the bobbin race. Turn the hand wheel slowly so you see the bobbin case is in the bobbin race properly.
Now, use totally different thread. A different spool and a newly wound bobbin. It can be any color because you are just going to be sewing on scraps till you get it fixed.
(Be sure you are using the bobbins that came with our machine or one the same size. If not, that can be a problem all by itself.)
Put your tension back on 4.
If you are getting nasty stitches try your test strip with a longer stitch length and see if that changes anything.
If you did all this and the stitches are still nasty send me a pm and I will give you my phone number. It might be helpful to have someone to talk to as you are doing it.
Beginning your post you said it was sewing good on your quilt and you pulled your quilt out. That might have pulled the bobbin thread out of the bobbin thread path but you should have overcome that the next time you threaded the bobbin thread in the bobbin case.
I will check back in often for awhile.