A year of loose, poorly absorbed stools with weight loss and nutrient deficiency is more than ordinary IBS, and it deserves a proper work-up rather than trial remedies.
The basic panel I would start with is CBC, ESR,
ferritin,
B12,
vitamin D,
thyroid profile, coeliac serology (tTG-IgA with total IgA), stool routine with fat globules and a stool test for Giardia.
Coeliac disease, giardiasis, lactose intolerance, small bowel bacterial overgrowth and thyroid problems are the common and very treatable causes at your age.
Meanwhile take small frequent meals with protein in each, curd or a probiotic daily, and try two weeks with less lactose, caffeine and oily food to see if the stools firm up.
Anxiety truly amplifies gut symptoms, so regular sleep, walking and slow breathing are part of the treatment rather than an extra.
Please book a consultation with me on Practo with your reports and weight record, and we will pin down the cause and correct the deficiencies properly.
Next Steps
Get CBC,
ferritin,
B12,
vitamin D,
thyroid, coeliac serology and stool tests done, keep a two-week food and symptom diary, and review with the reports.