I've been constipated for years?!

Start yourself on a high fiber diet,and for now you can take an over night laxative along with a stool softener.I have this same problem myself,and I've had to introduce more fiber into my daily diet,and the occasional over night laxative/stool softener.Hope everything comes out ok...'comes out' kidding.I do hope you start feeling relief soon.I know how uncomfortable it can be.Take care.

Tight muscles in your back can be pressing onto the nerves going to your butt so they aren't really responding to what you want, the message is blocked out and the pressure on the nerves keeps things tight. To get rid of the problem free up your back muscles to get the pressure off the nerves and then drink a big glass of water and you should be good to go. Here's how to free up the muscles in your back:
Back:
(do from a sitting position)
Place your left hand on your left leg next to your body. Place your right hand over your left shoulder, fingers over the back and the palm in the front and firmly pull down on them and hold. After 30 seconds slowly lower your body forward and to the outside of your left leg, keeping your left arm fairly straight as you do. When you reach your lap remain there for another 10 seconds, release the pressure but rest there for another 30 seconds. Then reverse your hand positions and do your right side.
For best results relax your body first by taking a deep breath and exhaling then remain this relaxed.

Look into your diet firstly. Are you eating enough soluble fibre? Good amounts of veg & fruit? Are you drinking plenty of water? And do you get enough exercise?
Go talk to your doctor to check there isn't a medical problem. Otherwise, the issue could well be just your dietary habits :)

dear do the follwoing

see a dr to get your self screened for hirschsprung's disease.
take lots of water and fluids
high fiber diet
lots of fruits
do not push so much while passing stool.

good luck.

mind and experience