Leg cramps, shaky fingers, no weight gain with a malabsorption history - that reads like iron,
B12,
vitamin D and magnesium running low, and worse before periods because of blood loss. A generic multivitamin will not fix that; you need to know which one is deficient. Get CBC,
ferritin, B12, vitamin D,
calcium, magnesium,
TSH and a coeliac screen (tTG-IgA) since IBS-labelled malabsorption is often undiagnosed coeliac disease. Then replace only what is low, in proper doses, with high-protein small frequent meals.
Next Steps
Do those blood tests before buying any supplement. Share the reports with me on a Practo consult and I will give you a targeted plan for the weight and the cramps.