Dont give drugs to your cat.
How are we supposed to know if you did something wrong if you don't provide any details?
Anyway, lots of people don't feel very high their first time. Have you used opiates before? The "high" is not super intense, it's often kind of an acquired taste. Feeling sleepy, pleasant and warm. Also who knows how pure it was or how much you used (or whether it was even real). My recommendation: stay far far away from this drug, especially injecting it. Read some of the stories on here about heroin addiction.