Struggling with constipation & lack of periods for a few months already

Hello, I decided to make this post because I've already booked an appointment to a doctor, but I struggle with health anxiety and I feel like I really need to vent because I'm just scared.

So, basically, I'm 23 (F) and I've been struggling with constipation for about 3,5 months. It all started when one day the shape of my stool just randomly changed - from, let's say, "normal'' poop to large, round balls. at first i didn't pay attention to it, but then i noticed my stool actually changed. Sometimes I had problems with passing stools and sometimes not, normally I had the urge to poop, but they were always balls of poop. Sometimes i defecated with these balls every day without any problems, and sometimes I didn't poop for 2-3 days and then I had a big problem with expelling feces. I also felt fecal masses in my abdonmen - I'm slim, and i felt a "row" of several balls in my lower left abdonmen, which disappeared after defecation and then came back. At first i thought that it was because of my poor diet - because i must say, it's not perfect. I eat fast-food once per 2 weeks, I don't drink enough water, I eat little fiber, little vegetables and fruits, and so on. I also often undereat and eat a little, my meals are very irregular too - so i decided to change it. I started getting hydrated, eating a lot of fiber, fruits, but nothing changed. My physical activity is also minimal, I mostly sit, sometimes go for walks, so I started walking more - also nothing. I even tried purgatives because I haven't had diarrhea in at least 4 months, but also - nothing. A very important aspect is that I live under constant stress - I'd say almost all the time, i struggle with anxiety a lot and I tend to stress over almost everything.

Besides that, around the same time, my periods stoped. I'll just say at the very beginning: I'm not pregnant, because I'm not having sex. My last period was in december. I already have an appointment with the gyneacologist. This isn't the first time this has happened - my periods are generally very irregular. In the past, I didn't have my periods for three months at least several times. I've been to the gyneacologist to check it, I had my hormones checked, I had a gynecological exam as well - everything turned out to be fine, so the doctor said it was stress-related.

Regarding medical tests, I also had blood tests and abdominal ultrasound 7 months ago, everything was fine.

Today, however, something happened that made me very scared. I had a very big problem with passing stool, I had to put a lot of effort into it. After some time, I had to go to the toilet again, and on the toilet paper I saw brown mucus with two small pieces of blood. I got terrified, there was very little blood, it was red, I'm not 100% sure if it was blood because i ate beetroot soup for 3 days. But I'm afraid it was blood after all... It happened after I had to put a lot of strength into passing my stool, so I thought it might be some sort of injury. But i got scared. I am very afraid that it might be colon cancer. My grandma died of colon cancer, she became ill after the age of 50. She had previously struggled with polyps. My parents are healthy in this respect, their test results are good, my mother only had one polyp, which was removed and did not come back.

I know that colon cancer at such a young age is very rare, but still possible. Unfortunately, I read articles about people my age who got sick, and now I'm terrified.

Overall, I feel good. Sometimes my stomach hurts, just in the lower left side, but it is a very mild pain, on a scale of 1 to 10 I would rate it as 1, sometimes it's like a squeaking, burning sensation, nothing strong. I've never had blood in my stool before, I sometimes bloat, I don't have night pain, I'm not anemic, I haven't lost any weight.

I have an appointment with a gastroenterologist in less than 2 weeks, I'm also going to get a referral for a colonoscopy, but I'm very scared. does this sound like something dangerous? Could it be due to diet and stress?