HI..first congratulations for having baby..
Dont be stressed. In female especially in your age group there is high possibility of having false positive stress test
since you are asymptomatic, no diabetes
, ECHO normal risk is very less..
Therefore dont be anxious take care your baby well and repeat the test after 6 months or one year after having good sleep in night and light breakfast in morning..there are so many causes for false positivity of the test