why it happens? cause of hormonal changes and your body is stressed. my view on this is going to be very different than other opinions but listen close. when your body is stressed the worst thing you can do is stress it out MORE right? when you eat food that is what you are doing. some foods stress the body way more than others. so make sure you are eating high quality whole foods and if you aren't hungry then simply don't eat. your body will appreciate not being more stresssed. take a day or two off from the gym to rest, let your body do its thing and then come back strong. just imagine what pro female athletes have to go through