a full feeling in my anus, almost like a large lump..

Hello, im 27 and have been suffering from some issues that are quite frankly worrying me like crazy, and im really scared to go to the doctors to be honest because im terrifed i have cancer. I live in the uk i will run through everything as simply as possible, if ANYONE has any help i would appreciate it so much more than you know.

Im a 27 year old female and about 18 months ago started having some bowel problems, it started with vile smelling toilets and almost like diahhrea, though sometimes i can become constipate too. In all honesty i just tollerated it and put it down to my eating habits, im not the healthiest of eaters and eat alot of junk to be honest! It hasnt really got any better, but i can go through phases where my bowel movements are better. What concerns me the most is i have a full feeling in my anus, almost like i have a large lump inside and sometimes feel sharp pains down there, also pains going through my vagina, its really odd. I used some germoid suppositories for two days as i thought it could be hemmoroids, but it did nt work at all. Im so scared that is something serious. I do t have any rectal bleeding or mucus, my stools can sometimes be a mix of pale coloured diahhrea an a stool that is harder and darker in colour. I have been experiencing some pain on my lower left hand abdomen and just above the top of my pelvis on the left hand side, it idnt severe, just quite uncomfortable. Bowel movements do help 8 out if ten times, but not always. The thing that worries me most is the feeling of having a lump inside my anus, i trully am scared. It feels like when i do pass stools it is having to pass by something.... If anyone can help PLEASE do, im desperate xx