Hi,
without any picture or closer description, it is hard to say anything. Maybe it's not that bad at all.
IF there is really reason for "mullet alarm", i.e. if your hair is very long in the back, while the top and front don't seem to grow much at all (frequently a deceptive impression), you could go for a single 1 to 2 inch trim "strictly at the bottom of the back only; no thinning, and no layering at all, please." Make sure it is a stylist whom you can trust.
Generally, we advise against trims if you want to grow your hair.
Hans-Uwe
You will eventually get exactly what you want if you say exactly those words.
Cut it off and put it under your pillow. The next morning, whether the Mullet Fairy leaves you money or not, you will not have a mullet!
Bill
Mullet Fairy??? I knew something was missing in my life!
In the early stages, it may look like a mullet. That's because the hair on top is still just "there on your head", whereas the hair in back is now spilling out around your collar and the back of your neck.