Sometimes I will sell and buy back in lower price, but look at current situation I will wait untill end of this month or more, still trading when loss just make my situation worst.
Yeah, trade at now very bad, we not know when is lowest price can buy or when we sell this coin, it will recovery and reverse

This is not right to make the trade. But this is a good time to collect more coins for future purpose. Not only bitcoin all other altcoin prices also went down, and it's still falling. If you wait one more week, I think the price still go down, and that is the best time to buy coins. At present don't sell any coin hold it in your wallet.
That's the right thing to do as you can see that the price of bitcoins has gone down and even majority of altcoins are going in downward direction so if you are looking to invest in any altcoins then better to wait for the next week and then start buying as price is tempted to go even lower in coming days.