There can be either weight gain or weight loss with celiac. The weight gain is believed to be in large part from hypothyroidism as iodine absorption is inhibited. The other factor is believed to be from the body being put in to a starvation mode leading to the body storing more fat.
But there are a number of reasons for weight gain including low thyroid, hormone issues, liver toxicity, stress leading to increased cortisol and lowered T4 to T3 conversion, hypothalamic dysregulation, diabetes, PCOS, overeating, medications, brown adipose tissue to white adipose tissue ratio, etc. I would really look more in to your history before jumping to the conclusion of celiac especially if there are not other symptoms present. I suggest first looking back to when this started exactly and what changed at that point including other symptoms. Acne? Increased facial hair? Mood changes? Fatigue? Depression? Increased stress? Changes in medications? Increased urination?................ The more blanks you can fill in the more likely you will find the root cause.