No Cpap Satisfaction

I've been using a CPAP machine for a year and a half.  I used the sleep pillows with a Swift Light for Her, a Red chin strap and taped my lips shut with paper tape from the medical section of the drug store.  It gave me what I needed with air pressure of 10 cm, but when I put on weight and had to change to 13 cm, nothing helped me.  So I was given a full-face mask, but it never sealed completely because I have little "meat" on the bones of my face.  I keep going back and being refitted for the next suggestion from the provider, but four masks and a few chin straps later, I'm still unable to get the benefits of CPAP that I had before my machine was recalibrated for 13 cm of pressure. 


I'm falling asleep driving to work and at traffic lights but can't find the right head gear to give me uninterrupted sleep.  Does anyone have any other ideas for me?