I'm so tired all the time - how can I beat it?

Despite getting plenty of sleep at night I feel so tired during the day. People have told me to cut out caffeine and sugars but I feel even worse without them as my body 'crashes' and I have energy crisises. People have also suggested doing exercise but I just have no motivation or energy to do anything. I've put on a bit of weight (about half a stone) despite not changing my eating habits or behaviour, am really super constipated, keep waking up in the night needing to pee but apparently having an almost empty bladder, keep waking up in the night shivering with cold but drenched (sometimes to the extent where I need to dry off with a towel and change my pj's) in sweat. I feel so utterly run down and really want some help/ advice please. Has anyone else experienced anything similar??