Hello, Welcome to HCM and thank you for your query. I understand your concern. Since you have persistent back ache at such a young age, it is important that you should have it investigated rather than keep taking pain killers regularly. The side effects of Sumo can be heartburn, abdominal pain or cramps, nausea, vomiting and diarrhoea; skin rash, pruritus, oedema, headache, dizziness, drowsiness; hypersensitivity reactions (e.g. bronchospasm, rhinitis, angioedema urticaria); GI haemorrhage/perforation; bullous/erosive stomatitis, purpura, thrombocytopenia, toxic epidermal necrolysis, haematuria, oliguria, and renal failure; increases in liver enzymes. Potentially Fatal: Fatal hepatitis, Stevens Johnson syndrome. If you have more queries, I am available. Take Care, Dr Noble Zachariah