Persistent digestive issues, mucus in st

Doctor, I am 19 years and 1 month old (DOB: 10/05/2007), 173 cm, and 40 kg. I am seeking expertise for a chronic digestive issue hindering my development. I grew until 15, stopped, then resumed growing at 17, gaining 6 cm by 19. In 2024, chronic diarrhea began; I managed it with non-prescription Enteroquinol. In 2025, while taking multivitamins/Omega-3s to support growth, I had a severe flare-up: mucus in stool, urgency, and multiple movements. A doctor’s 1-week course and gluten-free diet/kichdi resolved this, but 10-15 days ago, the mucus returned. I am concerned about underlying inflammation (like Colitis) or malabsorption. Given my history and growth pattern, what diagnostic tests (e.g., stool analysis, blood panels, inflammatory markers) do you recommend to identify the root cause so I can establish a long-term gut-healing protocol and finally absorb nutrients properly?