If you go on a strict diet, you will eventually not only regain all you have lost but gain even more - it is very important to eat normally, every day, always, without exceptions. Going on a strict diet will likely produce a short term weight loss followed by a long term weight gain. Avoid it like a plague - eat normally.

If your boyfriend tells you that you are beautiful, and, if he noticed your weight gain, that means that he simply finds you beautiful at your current size - so, rejoice.