I am almost 40 years old and the last couple months I have noticed my periods messing up. One period was little long, and then last month normal, and now this month I am 2-3 days late. I had a tubal about 6 years ago so I can't be preg., I have been on phentermine for weight loss last two month.(when all this started) and as of now have lost over 40 lbs in two months time. Had a pap a month ago when I noticed the one long period, and pap came back fine. So now I am wondering why after all this time my periods would mess up. I am months away from being 40, why all of a sudden and what should I do next?