First, that is not a too-bad problem to have! Short answer, I find that edging is a central practice to developing my (M) sexuality. In order to get more aroused and to experience more, you want to last longer; to last longer, you have to learn to slow down, stop, grab firmly, breathe longer and slower, or otherwise change the rhythm or ways you stimulate yourself. There is huge literature(?) available about edging.
You could also try a different posture (I'm partial to standing, as I can squat down to increase
the flow.)
The long answer, what I wanted to write about these last few days. I realize that through enemas, I've been able to develop an important part of mature sexual response, and one that has much in common with the patterns of arousal and orgasm in women. Around the pelvic floor near the pubic bone where the genitals are, there is a lot of spongy tissue, muscles and nerves. The prostate is there, full of potential. The filling and especially the bearing down, after or in between bags, brings a lot of pressure against the prostate, and stretches/stimulates the pelvic floor muscles. (Bearing down with a full belly can also influence the lumbar part of the spine, regulate the tone of the erector muscles and all the flexor muscles around the abdomen, and create more awareness of the pelvic region-so health benefits, too!)
Bearing down during the expel phase, especially during the "dry" part of the expel (you push and nothing comes out), the abdominal pressure can start a flow of fluid, a few drops or dribble of convenient, erotic natural lubricant, welcome appearance at the penis tip.
As you wrote: expelling (e.g. chunky pieces!) can also be pleasurable, waves of excitement in the pelvic floor,
prostate and genital. Together (often what I experience) a desperate hunger to have another filling. Which seems somehow feminine principle, to subsume myself to the sensations of filling from the bag.
The other day I got off rubbing the shower head, pressing it against the prostate. I'm not sure if it was a pure prostate orgasm, but certainly prostate-dominated!! :-)
The pleasure of being full, to me is so amplified when I bear down, and spikes so high that I can't compare it. Makes me crazy, into a complete enema slut!
I feel mature, in a way that I can have access to as much extreme pleasure as I have an appetite to take. While I love sex with others, I find with my enema-edging a kind of sexual self-sufficiency, a feeling that I can satisfy myself in a profoundly feminine way, that is as important me as my yang urges.
-P