Although missing the odd period is not unusual, the other "symptoms" are not. I'm sorry I can't suggest what may be wrong as I'm not an expert. But don't accept being fobbed off by doctors who cannot find a diagnosis and therefore conclude that there is nothing wrong with you. You know your own body and should continue to listen to it. You clearly believe there is something wrong, so I would say keep trying to find out what's up, whilst continuing to take care of yourself well.