Enemas can be intense experiences, and as a result an occasional side-effect is anxiety, especially in newbies.
The recipient must be reminded that everything is fine, that cramps (if any) will go away soon, and that mild nausea (if any) will also go away soon (eating something will help the mild nausea go away.)
For some, the experience can be therapeutic to unload worries, etc. (in other words, to [color=#993300]put to good use the breakdown of their psychological barriers attained thanks to the enema, etc[/color].)
In rare case, the recipient might throw up a little. That seems to happen about once every 100 enemas, in my experience, especially in cases of larger enema amount, relative to person size.
Rare as it is, the risk of throwing up is an excellent reason to [color=#993300]avoid closed-mouth gags during enemas[/color]. In virtually all the 150+ enema films I've shot so far, and in my personal life, I've almost always used OPEN mouth gags in cases where the enema recipient is gagged.
I also think that open gags are superior to closed ones, but that's another story... 😉
PS: I won't repeat the cautions mentioned by others on this thread
PS2: @Unsure, my guess is that your symptoms were due to anxiety (assuming that you're in good health and didn't do excessive enemas.)