BTC shot up so high so fast in 2017 because it was overly hyped that even people who don't know a single thing about it just registered a Coinbase account and did a buy order.

So you're question is: "Why.... it is not boost up again.......". Simple, it's because not that much people are buying bitcoin. And if you're not willing to wait for another price rise that's hopefully a lot more sustainable, then go sell your bitcoin. Investing is not for the impatient.