Just a thought....if I'm reading right, you have 3 layers, denim, flannel and cotton...Some people only use 2, the denim and then flannel or cotton for the back, if you are using 3 layers, the middle layer can be cut smaller, then before stitching your blocks together you do an x pattern over each little "sandwich" or a heart or a circle if you want to be different! That way, you only have 2 fabrics to sew through on the seams, but still get the warmth of the extra bit in the middle and the middle stays put because of the anchor stitching (oh, and dont go right to the edges if doing the x's, because you want your edges to fray nicely.

Hope this helps....you may already know this...so hope I'm not being too forward...Hang in there and please don't let this get you down.