I was referred to a nutritionist for celiac's disease, is it worth going?

Why not?: If there is minimal cost to you, it's a good idea to tap into as many resources as you can. Even if you get just one good idea or bit of info that you wouldn't have gotten otherwise, it will have been worth it.

Yes: Gluten is hidden in many foods, with the help of the nutritionist you will learn where (and under what names). With this knowledge you can get the disease in control sooner.