I can understand your reluctance to try an enema again following your unpleasant experience with the Fleet chemical disposable, but there is no comparison between that and a gentle natural enema using an enema bag.
I tried a Fleet myself once, only once, and never again. I suffered very intense and lasting cramps, and just as bad, terrible burning sensations whenever I would release any of the chemical solution. It caused me to have a lot of gas pains, but failed to get out very much stool, if any.
I was in high school at the time, and when my mom got home I told her what happened, and she got out the enema bag and gave me a plain water enema that stimulated a welcome release and ended the gas and the horrible burning sensation around my anus.
So I encourage you to give a natural cleansing enema a try. I can guarantee that you will not experience anything remotely like what you did with the Fleets. Go slow, take only as much as you can without excessive fullness the first time and I expect that you may be pleasantly surprised with the results.
With an enema, you get to time the results to your convenience - no surprises.