It'll get easier the more you use it. I was in the exact same boat as you four weeks ago (you can check my posts), now I can hold almost the entire 100ml for the whole night (8 hours), though with a bit of discomfort near the end of the 8 hours due to gas building up.
When I first started, I used as much as I could get in comfortably, which is a small half of a bottle, then went to bed on my left side. At first I read to distract myself from the discomfort/urge to go, but later on I just fell asleep. On most days I wake up 3 hours later to evacuate to enema along with gas and poop. Occasionally I would have a bad day and either evacuate it after 1 hour or end up not being able to fall asleep for 3 hours because I was feeling terrible. Eventually I increased the amount of enema (small half>2/3>as much as I can) because I got better. I don't know about
you, but my symptoms got worse the first 1 or 2 weeks I started using Pentasa (4g/100ml), then they got better to more or less pre-Pentasa state (1 BM per day with bloody mucus).
Before you use the enema at night, prepare everything to go to bed, so inserting the enema is the very last thing you need to do before actually getting into bed. 20 minutes before using the enema, empty your bowels as you might has some gas, mucus, poop, etc and adding the enema will probably make you feel more full. Allow yourself/your body to relax a bit before the enema. During your pre-enema prep, keep the bottle of enema on you to warm it up (surprisingly the room temp enema never really bothered me). Squeeze out the air from bottle before inserting because extra gas is no good.
Also stumbled across this: http://itslikethisuc.blogspot.com/2013/01/retention-enema-tips.html
Post Edited (k1002) : 1/6/2019 1:00:18 PM (GMT-7)