My 4 year old son does not want to go out for any outing with us?

My 4-year-old son does not want to go out for any outings with us. He is very sharp, very vocal, very observant, doing pretty good in school, not introvert at all, interacts with everyone known to him, and tries to make friends with unknown. He used to love going out with us about 2-3 months back and in fact used to pester me to take him to malls or other places. however for the past 2 months he does not want to leave home. He comes up with excuses (very intelligent ones) for not going. If i present a situation to him indicating that he would have to come with us as there will be no one at home (so that he comes with us), by telling him that my parents have to go somewhere, the maid has to go on leave and we have to go to his favorite mall, he will come up with alternatives and refuses to leave home. His only outing apart from his school has been limited to the park where he loves to go and wants to go. He also does not want to go to any other park apart from his usual one. Our offers for ice-cream and chocolate, McDonalds (anything) too does not make him come with us, nor does he wants to go out with my parents. Please help me as i have never heard of a situation like this from anyone else. Do i need to show him to a doctor? -- Guys please help -- Kapil