Anna17xox, I am guessing that you are 17, by your name and reference to pediatrician. Farmer smith and others have given you great advice. I am 65, with formal diagnosis of CIC 17 yrs ago. I am older, with many medical issues that can lead/cause chronic constipation. I could write a book about my own 💩💩💩 experiences. You mentioned maybe blood, you really need to rule this out, now, and for certain. I don't know if you being young can rely on the box test, Cologuard.
Your pediatrician is right about taking this to the next level and see a GI. However, most, specialists are likely not willing to really get all the answers for you. So, if you go to a GI, ask lots of people for advice on choosing a GI. I was with my GI for 18 years, he was terrific at first, diagnosing me with lifelong celiac disease, since I was and still am asymptomatic, he was very proud of himself for the diagnosis that shocked everyone. But 17 years of trying to find the cause of my CIC, my body has responded to nothing for any long period of time. He literally dumped me after 2 x-rays showed I was probably forming a partial small bowel blockage, he disagreed then he had me have a CT scan, that proved him right, no blockage forming(I had stopped eating almost all solids and drank high grade meal replacement shakes and even more water than the large amounts I drink always)... but showed I had a redundant splenic flexure(this is 99.9% congenital and often causes no problems, but it is causing me problems and pain)). 3 months later I was in the ER with a partial small bowel blockage. We all define 💩 differently. I would stop the Metamucil/fiber and use the miralax or drop back to a stool softener, depending on what your CIC is like. I am retired, so I have the luxury of putting my body into full on diarrhea for days to see just what comes out. This may not be an option for you. Also, you can have almost normal poop or diarrhea flow over fecal impactions. Ask your pediatrician for an abdominal x-ray, standing and laying down. This will show if, where, and how much, you have fecal matter retention. I came up with this idea when my GI just kept hitting dead ends with my treatment. I have them every few months, for 10 yrs..only 2x in 10 yrs I had normal amount.(except for during a colonoscopy there is always some fecal matter in the colon). So, every other time I had moderate to severe fecal load, in @ least 2 of the 3 parts of the colon, usually all 3 parts. In my humble opinion, you are WAY too young for this CIC. Two last words: If you are straining, something is wrong; if you are having forceful/explosive gas and poop, something is wrong. I truly hope you can find a great dr. You deserve to feel good and live life without this.