to make the best decision for both of you. be honest about how you feel. you have a lot to consider right now. if he is genuinely concerned about whether or not he is responsible for this pregnancy, he deserves more information.
tip: if you are the father of the pregnancy, try to take some responsibility for the decision making process–get educated, talk to your support people, think about your personal situation, values, and beliefs. ask yourself some of the questions listed above. be honest and true to yourself.
whether this was planned or not, your parent(s) would probably really like to know about a pregnancy. consider telling him/her sooner than later. 