How long does one wait to try to become pregnant again after 2 years of coumadin therapy?

I was diagnosed with an intermediate pulmonary embolism via a V/Q scan 1 year after having a baby. I have never taken birth control pills so the cause is unknown. At one point, while on coumadin, I was tested with elevated level of lupus anticoagulants. I decided to check with another doctor who put me off coumadin for 3 weeks then rechecked my blood. All tests came up normal-no abnormalities. Although I am not sure if exactly what I had was really PE and what actually caused it, how soon can I get pregnant again and what are the preventative measures I should do...Thanks!