There's no way to tell the end of a rally, otherwise, we would all be rich by now. But some advices, don't use coinmarketcap as a way to know the actual price, they usually use some inflated market price and use it in the average price, which ends up with a price that differs a lot from most of the major exchanges.
But most importantly, you need to check the charts constantly, look for some real-time btc charts (or any cryptocurrency chart) and try to keep up to date with the prices.