Is it just a seasonal change or is there a serious problem?

My normal system that usually works like clockwork has been completely turned upside down for the last two months. I've been late for a week, but I took a test and it came back negative. I'm saying it's stress, but there's also an unease inside me. My body is swollen, everything hurts, but nothing is happening. Should I wait a bit longer before going to the doctor, or should I just go straight away? I'm really feeling down.