Mining profitability is based on the current Bitcoin price and mining difficulty.
Mining difficulty increases about 5% every 2 weeks or 2016 blocks, but may vary based on global hashrate.
To get the most out of your hashrate on the Bitcoin.com mining pool, we highly suggest that you activate "auto-profit switch" on your account. When activated your account will automatically switch to mine the most profitable coin (BCH/BTC)
You can see a mining difficulty compassion chart for BTC and BCH here: https://bitinfocharts.com/comparison/difficulty-bch.html
We have a great site to see the Bitcoin (BTC) ecosystem at a glance here: https://charts.bitcoin.com/
If you would like to see past BTC mining difficulty history, please have a look at the stats on the bottom of this link: https://bitcoinwisdom.com/bitcoin/difficulty