Of course, you can call the police any time you want. There are some questions that you should ponder however: why don't you simply leave the house? Why are you living with a felon, are you also a former felon? How is this person related to you? If there are drugs and children in the home, will you also be charged with child neglect or endangerment if you tacitly consented to the drugs (and constructively possessed them)? Are the children yours; will they be taken away by CPS if the police go into your home and find it uninhabitable and unsafe for children with drugs strewn around the house? Don't provide answers to any of these questions on this public forum. If you can afford it, you should retain an attorney to help protect you and your interests in this matter. If you can't afford an attorney, I would seriously consider simply leaving the house. Interacting with the police is the like playing with fire, sometimes you get burned. Best of luck.
Look at the following link for forms and info about getting a domestic violence restraining order (no filing fee): http://www.courts.ca.gov/forms.htm?filter=DV. Many courts provide help on getting these done right, but the link above also gives info. Also ask the police about getting a restraining order or a criminal protective order. Make sure you aren't doing anything illegal when they come; you don't want this to backfire on you.