Norethisterone

Hi all, i have irregular periods and today my doctor prescribed me Norethisterone that will help regulate it. I have researched about it, and it seems that it actually causes weight gain, Has anyone of you managed to keep your weight under control despite being on this pill? I am supposed to take 3 pills (5mg/pill) daily for about a week and see if it comes. My doctor may want me to take it for a couple of months, which i am pretty reluctant should it really cause any weight gain. Please advice!!