I will be wondering that why the price of BTC don't be constant , it keeps changing

Well price of btc is very volatile because of the ups and downs of bitcoin , one of the factor why bitcoin is too volatile because it's very decentralized , which means no one can control the price of bitcoin , not just any other currency for instance the currency we have like usd or pesos it's been controlled by government which they just agreed on one price.
And it's somehow a good factors that's why many people investing on bitcoin , by a chance to be a millionaire.
And when you are so smart can you tell us what are this ups and downs? Fluctuations in the first place means that price is going up and down! Your comment Hans doesn`t have sense, so much that I can say it`s stupid. Just yesterday I were saying how many people here don`t want to invest a bit more time in reading before they make a comment and you are one of them!
Read more, think about what you read, learn and later start to talk. Price of bitcoin depends from supply and demand, you can ask what affect supply or demand, but that are other kind of answers. I hope you will try to learn something or you will be kicked out from this forum cause of your stupidity.