Don't know what to do

I just realized today that my diet isn't working for me and I need to up my calories so I can gain weight. I started out 118lbs. I weighed myself this morning and I'm 115, that is very unhealthy for my height. I told my mom I want to see a nutritionist. She wasn't concerned one bit about my weight. Told me to not worrying about upping my calories and to lift weights because muscle weighs more than fat. While that is true, if I don't eat enough while working out I don't think that is going to get me anywhere.

Maybe I get why she's not thinking about it the way I am because she's on a weight lose journey and I'm trying to gain weight. It's two completely different diets. My lowest weight was 113lbs 4 years ago and I don't want to go back to that. I want professional advice, but since I'm on their insurance if they don't think it's necessary I can't do it.

I'm just so frustrated. All the calculators and all the apps are telling me between 1700 and 2000 calories. I've been eating over 1800 almost every day. It's hard to eat a lot for me since I never have an appetite. I'm confused and frustrated and just want to give up. So many different apps, calculators, and people are telling me so many different things as far as calories, carbs, fats, and protein go.

I just want professional advice it's driving me crazy.

Anyway I apologise for this rant. If you have anything helpful please comment