Off For Two Weeks

I have been taking Phentermine since June 8th and have lost 17.30 lbs.
Last two weeks or so it has not been working as well as it did in the beginning. It is harder to stay within my calorie limit.
I have still lost weight but my weightloss has slowed down dramatically compared to the beginning.
I have decided to take a break for two weeks and restart it later.
Last weight 128.40.