What could be a reason that MS contin (morphine) makes me sick?

See below. All opioids (pain medicines) have this effect on some people. Morphine tends to cause constipation more so than others whcih may worsen the nausea.
MS Contin (morphine) Nausea, vomiting, dizziness are common side effects for this drug. Try to prevent dehydration if n/v frequent or severe. Discuss matter with prescribing doc for possible alternative drug.