You can buy sharpeners for your rotery cutters. they ar around $24
I know that seems expensive but they really do work. Or use your Joanne coupons to buy the blades. I wouldn't use a utilty knife or any thing like that on your fabric and it will ruin your mat and rip up your fabric. The only other thing you could do is go back to use scissors and cut everything by hand if you don't care about accuratcy, or time it takes. but I wouldn't waste the money on any other tool. Good luck I know You get frastrated. Donna