My body feels pregnant?

So far it's been all negatives, but I still haven't gotten my period. I found with my other 2 pregnancies my body would feels so exhausted like I had been a big walk up a mountain, or when you go to the gym and over do it then wake up the next day and your body just feels tired, and you could just lie and sleep at 12 in the day. That's the way I've been feeling the past nearly week now, my second baby is still up during the night and now I feel as I've I'm starting to get really tired again and can't wake up when I'm usually fine. Has anyone else experienced this