First off, a bit of background on myself and my health history! I've recently qualified as a nurse (and worked my butt off to get to this point!) but have already had to take two weeks off due to my symptoms. I've suffered chronic abdominal pain for about 6/7 years, accompanied with nausea and acid reflux. I was referred to gastro, who did an endoscopy with no significant findings and as this was about the time I was also diagnosed with PCOS, they opted to discharge me as they believed it was a gynaecology issue. I then had a laparoscopy to explore the possibility of endometriosis, but once again there were no significant findings. I was discharged back to my GP, who have been trying to tell me my symptoms are IBS and anxiety. 
Now to get to my real point! The past three weeks my health has gone really downhill, my stomach has just been in searing pain, which is leaving me laid up screaming and shaking, unable to move. I've had loose stools for two weeks and most of the time, this is instantly after eating. This is sometimes relieved with loperamide for a day or so, but both movements are incredibly painful. I've had blood and mucus in my stool. Pulse changes (pulse drops as low as 45 and then as high as 145), with a BP between 79/50 - 106/84. I've been getting this horrible feeling of pressure in my abdomen, almost like there's something there but I just can't feel it from the outside. I've lost 8lbs in two weeks and haven't even had to the energy to get out of bed to sit on the sofa. Alongside my abdominal issues I also have joints and bones that become very painful (e.g collarbone and a small joint in my sternum), shooting nerve like pains in the vagina and anus, pain during sex. 
I decided enough was enough the other week and opted to start seeing a well known GP for ongoing care as this has been affecting me for years. She won't see me until Monday and talked over me whenever I tried to explain symptoms, saying "you were diagnosed with IBS, has that not been made clear to you?" And "you're 24, there's clearly nothing serious wrong with you". 

Feeling really defeated, dismissed and just scared. Am I justified in being concerned? I feel like I'm just being a nuisance to my doctor!