I had my period twice this month first one was on aug. 4th and was normal period then on the 29th of aug. i got it again what can that mean?

Likely normal: A cycle length (from the first day of one period to the first day of the next period) of 21 to 35 days is considered normal. Since calendar months are 30-31 days, it is common to have your period on a different calendar day each month. So if you started a period on Aug 4th, you could easily get a second period as early as Aug 24th, and that would be normal. Cycles less than 21 days aren't normal.