Gaining Weight Fast

So I've been working out and eating better a lot make than I used to this past month and I have gained about 15 pounds. And not in muscle, I have noticed that I'm getting chubbier too. I'm really confused and discouraged. There's no way I could be pregnant. I honestly have no idea why I have started gaining weight this fast when I have started to live a healthier lifestyle.. has anyone had any experiences similar to this or have any ideas as to why this is happening? Thanks 😕❤