Kudos to you for your toughness!
For the average person, we would recommend that they go for no more than one hour increment maximum per week. This way it will allow the body to recover and adjust to new heights. And it is very important to walk for at least half an hour a day. To go for long sits too fast could cause hyperextension of the knees.
Some types of pain are acceptable and should be endured, some are not.
Overall, do not try to force it. We all can only go as fast as our blessings enable us.
As you have discovered you ran into your own limitations and need guidance. If you wish, please give us a call so that we can get to know your personal situation. We will also be able to give you advice that is tailored to your needs. Our temple telephone number should be on our web site.
By the way, long sits in the tens of hours should be done under the supervision of a trained Chan Master.