What am I looking at, top or bottom? If top goes to the back, top tension is too loose or bottom is too tight. What type of thread is it? shiny type might need a bobbin genie, little cheap disk you put in the bobbin case. Is your needle large enough. I went from a 16 to 18. Is bobbin thread the same as it is in the top or bobbin thread thinner? Is the batting odd? Is the fabric different? Since the thread is bunching I think you might need a bobbin genie. Is the needle in the right way. there is a front and back on these things. sorry you are coping with this, so frustrating. Oiled the tension and the bobbin case a little?
what thread are you using? If it is isocord or glide you will need a bobbin genie or a spring. I could never get the spring to work for me but the bobbin genie did the trick.