Bobbin Thread

I have a Brother 700. My bobbin thread is doing all of the work. Everything is coming out white with a few lines of color here and there. I've tried adjusting the tension both ways and still nothing. Can someone please help it's really making me mad! Thanks!

Location: 
United States

Yes :D I agree cleaning the bobbin maybe the problem, but check if lint is under the area that the thread passes in bobbin...if this is happening adjusting the tension screw on bobbin will not help...it has to be cleaned thoroughly! Hold the bobbin in your hand by the thread only(like a yo-yo) if the bobbin falls to the ground quickly then lint is under the area I mentioned. It should have some tension when held in this position and should move very slowly down.

Good Luck
Pepe