Scared of colon cancer; 19 year old. Someone help please!!!!

Hey everyone, I know this might be a long shot but I didn't know where else to turn. I am 19 years old (20 in November) and I have been having blood in my stools. It first happened over a year ago and has happened a few times since; its always dots of bright red blood, mixed in with mucus (sorry I know that is TMI!!!!). I would have passed it off as internal piles or a tear, but it really is mixed in with the mucus. I went to my GP on monday; she thinks I have IBS. She has put me on a low FODMAP diet and given me necessary meds. She also referred me for a blood test and a stool sample to check for ibd or colitis, etc. I am still so worried. What if its anal cancer or cancer low down in my colon? I thought I had a mass in my lower left abdomen but I dont think there actually is one. I am afraid that the stool sample and blood tests wont check for cancer and it will be missed. I am beside myself with worry... I am to go back to her in 3 months for an update but im afraid that will be too late. Should I be concerned??? HELP!!!! :( :( :(