Antidepressant for IBS-D?

I had a colonoscopy 10 years ago (age 16) and was diagnosed with IBS. He told me to avoid certain foods and sent me on my way. After all of this time with no improvement I decided to finally go back to a GI specialist. He put me on 25 mg of nortriptyline ( a TCA ). He says although it is an antidepressant, it works as a nerve blocker in the digestive system and should help with all of my symptoms.

I struggled with weight gain when I was on birth control, and I’m worried about weight gain with this medicine.

I’m wondering if anyone has experience taking antidepressants for IBS and if you should share if it helped.

I’m also wondering if anyone could share their experience with this medication in general, regarding weight gain.

Thanks!!