Hey, I'm looking for advice as I'm growing more worried and don't know who to ask.

Since the start of this year, I've had a mixture of symptoms, from dull abdominal pain to sharp painful abdominal pain, blood when I poo, dizziness (especially when standing), brain fog, night sweats, and I am so tired all of the time and feel so violently weak (like I have weights on me and my organs). I've also had a fleshy, jelly like, bloody lump come out of me around 3 weeks ago now.

Originally it just started off with cramping, I ended up in hospital from how bad it was (I try to not go hospital a lot as the ones around me aren't the best and a lot of medical negligence happens). They tested my pee as they thought it was kidney related, and refered me to get ultra sounds for my urinary track and my kidney (as I also had UTI like symptoms that kept coming and going). As everything was fine, they said it's probably just hormones and sent me on my way. I left it for a bit as the pain wasnt too bad after that. 
I went to the toilet one day, and had blood come out after, it started off as a little amount, to some days having so much, on the paper, mixed into my stool and on the bowel. I went to the hospital/ walk in centres a couple times upon 111's instructions as it wasn't getting better, and there was so much of it. They all just said it was probably hemhoroids as I'm 18 and thats 'too young for it to be serious'. Eventually, I turned to one of them and explained that so much is going on, I'm autistic and I'm getting worried, asked if they could just have a look to check it is hemhoroids, they checked and said 'it probably is just coming from that'. I asked them if they could be sure as 'probably' isn't too reasuring, and eventually got sent to my GP. The doctors also said that I'm fine as I dont have any melena. They checked, said I had a fissure and lump so they are going to refer me to a colonrectal specialist (obviously I had to wait for around 3 months). The bleeding stopped, came back and stopped again. I went, they checked and said that I have grade 1 really small hemhoroids, and that they want to do a qfit test to make sure thats whats causing the bleeding. They also didn't see any signs of a fissure (I was bleeding a week before going). At home I ordered FOB tests just as I'm impatient and wanted to see what would happen when I go back (as depending on the FIT test, i'd either get a sigmoidoscopy or a colonoscopy. I haven't had visable blood, and have done 3 in the course of a 2 week period, all of them are positive. The blood that I have had has been bright red, to really dark red and consistently changes.

I understand on a statistical standpoint that as I am young, it's less plausible that I have cancer, however I study biology and chemistry, so I like doing proper indepth research, and I really feel like it's not just from hemhoroids, and I've been dismissed so many times to get to the point I am at of getting help, I don't want to mess it up. I also am worried that if I keep advocating that something isn't right, and turns out everything actually is and it is just hemhoroids. 
If anyone has any information of has experiences simular things please respond.
Hope your all ok and having a good day x