Is it normal to have 2 days bleeding during period? During my teens it lasted for 4-5 days. I am underweight but I have no health probs.

Underweight? That is a health problem. One consequence in women who do not eat enough is a fall in estrogen, which will diminshes menses or stop them altogether! hyperthyroidism can also decrease menses or cause amenorrhea, and it too causes weigh loss. You did not specificy if your being underweight is chronic or recent!