Well if you still positive that bitcoin will boom at end of the year then now is the right time to start buying since its price has dropped again. As usual, most of us here predict that bitcoin will reach $20K at end of this year like what had happened in the last quarter of 2017. So invest now and let's just wait and see.
I think that when a property tends to go down in price, it is extremely difficult to determine if it has hit bottom or not to buy bitcoin. However, using technical analysis, we can at least give you a rough idea of the price, which can help you a lot. Remember that as the panic spreads, the downturn can surpass your imagination.