I'll have to begin by stating, I'm not a medical professional. On the other hand, I have been suffering from gastrointestinal issues for my whole life, roughly 30 years.
That being said, you need to see a gastroenterologist as soon as possible. If you have something like ulcerative colitis, diverticulitis, Chrohn's disease, or a number of other issues. Some conditions may require immediate surgery or just a cleansing and some medications. Either way, a medical professional needs to biopsy and analyze your stool. I would recommend you need an upper GI and a colonoscopy, if you haven't already. I was born with an underdeveloped colon and it has resulted in a life full of gastrointestinal and autoimmune issues. Often, diet alone can cause me to feel like I have a severe flu, I get aches and pains throughout my body, and suffer from chronic fatigue. GI issues are something to keep on top of, as they can degrade or improve your quality of life.
I have seen stuff like this in my own stool. Including stuff that looks like the long strands of mucus (which may be a parasite, I'm no physician). I was diagnosed with IBS, mild Chrohn's disease, and scattered diverticula. Since learning about it, I've radically changed my eating and drinking habits.
Before I went to the gastroenterologist I would be stuck in bed for half of each week. Now I have my health back, with little medication, improved energy and stamina, more drive, normal poop, and no more pain! I gained my life back with a few really quick and easy visits to a specialist.
I hope this was helpful and I really hope you find out what is going on. Best of luck, hun.