Finding a purpose in life isn't easy if there is no absolute truth to hang on to. However, there are other possibilities:
Is there something you are personally getting out of life?
Are there other people you care about who you help or who you can help (even if you don't know them personally)?
Is there some reasonable hope that you can eventually make #1 or #2 happen in the future?
At a minimum, there are people who care about you on this forum and want to help you. Even if the help they provide is not always very high, you probably care a bit about them in return, although in-person stress you experience may drown out those feelings. You are also able to help others here as well with your perspective, and you should not write off that potential. By your own accounting, your kids need you, too, and you can be an understanding ear when life gets hard for them.