Well, your going to have to do it no matter what. Although you and your mom are not so close babys do tend to bring people closer...
Don't expect anyone to be happy at first... If they are, thats wonderful. But telling parents that you are going to have a baby, is pretty shocking news, and your going to have to give them time to think about it. Since you are obviously going to keep the baby, don't be upset if they suggest abortion. Or even suggest paying for it. (we were ttc, and when we got pg we were offered this from both sides of the family, and we are 20 and 23) just give them time to think about it. And, also, don't get flustered if asked, and what do you plan to do?? Make sure you have a plan... Also, try thinking about finding a place, or whatever without needing the help of roommates... First off, how many people want to stay somewhere with a screaming baby?? Second, you don't want people around all the time, ie parties and stuff... Make sure you have at least alittle of this figured out before you even approach your parents... But, tell them before they find out on their own.