I gave birth to my 1st baby last jan 28,'06 via C section this sept '07 i found out that i am 4 weeks pregnan

i gave birth to my 1st baby last jan 28,2006 via C section this sept 2007 i found out that i am 4 weeks pregnant. my question now is it safe for me to be pregnant again? bcoz my doctor told me when i gave birth that i must be pregnant only after 3 years or more...am worried, what will happen to me? by the way i undergo C section bcoz i experienced preeclampsia.please help..thank u so much.