Too much nausea (percocets)

Ive only taken oxycodone twice. (5/355's) The first was 30mg+ some weed and very little alcohol. I was struggling to not throw up a lot of the time, but other than that I liked it.

Two weeks later I took 20mg and again smoked some weed afterwards. This time I was at a bowling alley with a lot of people. More than half the time I was REALLY struggling and trying to keep back from vomiting, when I got home about 5 hours later I finally puked.

Any ways to fix this? Would switching from percocets to oxycontin help?
I take them on an empty stomach, is that a bad idea? PLEASE help. :D