At your age, they won't really want to do a colonoscopy on you. Colonoscopies are meant for people who show very serious symptoms (not small symptoms here and there), are 40+ or have family history.
Tbh, you don't even need tests but just for your reassurance you can ask the doctor to do a complete blood count test, FOBT test and calprotectin test. However, even positive results on these tests can mean a number of things and not cancer.
I am having soft stools as well, sometimes they are normal. IBS or a sensitive stomach can cause it. Even anxiety can.
I know it is hard to believe me. I am the same as you, but I am trying my best to defeat my fears and so can you.