You mention how much water you used, but not how long you held it or which position you were in to do the enema.
I am no expert, but I have had tremendous success with doing enemas at home. Here's what I was told to do:
-begin a 5-week program, 1st week one enema per day before bed, 2nd week one enema every 2nd day before bed, 3rd week every 3rd day and so on... This will get you started and then after that you can determine what works for you.
-stand on hands and knees on the floor with a towel underneath, lower your head close to the floor so your bum is higher, do some nice breathing and try to relax. Then insert the enema tube and let water flow in until you feel full. The enema bag, depending on the length of the tube should be about 3 feet above you.
-once full, remove the tube, immediately turn over to your back and do a shoulderstand (yoga posture) for one minute. then lie on your back with knees up for 5 minutes. Then lie on your right side for 10 minutes. The purpose of this is to try to get the water to go much further into the large intestine.
-the first few times you do this, you may not be able to hold for the full length of time. If it becomes very uncomfortable and you have a STRONG urge to go to the bathroom, just accept that and release the water on the toilet.
After some time you'll be a pro. You may not have had success due to your constipation, or with not getting the water in deep enough. A professional colonic is much better but costly, so learning to do an enema at home is great and then you can have a colonic periodically.
Also, make sure you're using body temperature purified water. The above directions are for use with a water enema, not a coffee enema. The aim of a coffee enema is not to get the coffee in deeply and to clean the bowel, but to benefit the liver. For coffee enema instructions, see links on the Curezone site.