Is it normal to have two light periods in a month?they were 2 weeks apart. i never had this happen before this is the first time

It depends: Usually it should every 4 weeks but in the menarche time the periods are irregular due to hormonal dis-balance. If you don't think you are pregnant and this keeps happening, then you want to see gyne specialist.

No: Its not normal. There can be many reasons (hormonal, infection, physical factors, stress, etc). But if it never happens again it makes no difference. Would check a pregnancy test if that is relevant. Otherwise would just wait and see if the problem goes away.