Can anyone help me with a medical question?

I am a 28 year old female. Have been having an onset of symtoms for the past few months. It was my GP that referred me to a gastro specialist as he described me as visibly shrinking before his eyes. I have been feeling increasingly weak and dizzy, bad abdominal pains and sometimes my limbs are to heavy too pick up or move. I lost a lot of weight but am now forcing food down me and although still thin gaining and losing again. Also my head hair has been falling out in clumps. My test have come back clear for hypoadrenilism, addisons and thyroid problems. I'm having a barium meal in a week and half but my doctors away till then and have started feeling sicker as in weaker etc. Also my GP asks about black stools. What are they supposed to look like I need to know. Should you only be worried if they are completely black? My stools are very loose with small black wierd clumps in them, more showing up lately. Does that count as upper GI bleeding? Can't seem to find the answer on the net. So if anyone knows for sure be grateful if you'd let me know. Also if carry on getting worse should I get some help or just wait until my hospital appointment? Don't like to bother the medics you see! Thank you if anyone gets back to me.