New to This app

Hey I am new to this app. I have been told it is a great app to keep track of your daily in come. I was a size 8 2 years ago and i went up to a size 18 i am now back down to a 10 but the weight doesn't seem to be coming off anymore and i haven't changed my diet or anything. I go to the gym 5 -6 times a week for an hour each day in my lunch break. I am eating only Gluten free things. If there is any help someone may be able to give i am willing to try anything to get back into the size 8 dresses i have before Feb next year.
Thanks
Jacinda