You seriously, seriously, seriously need to tell your mom everything. That is not a healthy relationship at all. You should be telling the truth to your mom always. Your mom should not be mistreated that way from you or your dad. Tell her immediately.
The fact that he's still with you and you believe he still loves you is a biggie. People make mistakes and no one is perfect. One would hope that your dad will realize his mistakes and make the corrections needed someday. In the mean time, accept the good with the bad and deal with it.
You are blessed because you have Both a father and a mother to love and that you know both of them. You can learn from the two of them seeing their mistakes and dreaming of the perfect family. Caring about each other and simply at the consistent hope compassionate love that you feel