In the 7 years I've been doing this I've been between a size 10 to a size 18 and I've actually found I'm busier and have more regulars at my larger size. I've been confident in my body for most of that time, but at the times I was smaller I was actually quite ill, so feel and look a lot better now at a small 16.
CGIW and Rosie had some great tips about language in your advertising and your photos. I make sure my username on all my ads includes a reference to my shape.
Another thing I'd suggest is to surround yourself with images of women who look like you. Subscribe to body-positive feeds on social media, follow other BBW sex workers. It's very easy for our eyes to become accustomed to only seeing beauty in the standard size the media serves us as a representation of female beauty. We have to re-train ourselves to see the beauty in all different shapes and sizes (and ages, skin colours, visible disabilities etc.)
I also make a point of choosing, if I can, to support businesses which use models who are diverse in looks. For example Rihanna's line of lingerie, Savage X Fenty - they use models who are every size, every race, models with missing limbs, alopecia, etc.
Wear things that you feel confident in and embrace your curves. The clients you want to find will find you - you are their ideal. Don't hide your curves, just advertise honestly and openly.