There's a stereotype about atheists and atheism, that we're nihilists and that our world is cold and lonely. The thing is, atheism is neither inherently meaningless nor is it inherently lonely. As an atheist I don't see meaning the same way believers do because I don't believe in a god to impose that meaning. As for being lonely, that's a consequence of embracing a minority position. Atheists in largely secular communities aren't lonely because they're not being constantly pressured to conform to religious values. Do you think Christians in communities dominated by Islam don't feel lonely? Do you think Hindus in communities dominated by Christians don't feel like outsiders?
A common question asked by new atheists is "what now?" They've finally taken that last step and they've abandoned belief. They've rejected what they were taught to embrace for so long, and they might still be hiding it to avoid social backlash or they might simply be looking for something to fill the void. Imagine you've just kicked a bad habit, like gambling. You aren't checking the papers to see which ponies won, you're not attending weekly poker games and you're not practicing your dice rolls. Imagine these things previously consuming your time but now you don't know what to do with yourself. How do you cope?
The answer is: any way you choose. Go back to an old, non-gambling hobby. Pick a new one. Read up on new events or trends that might interest you. Get involved in a group that doesn't revolve around the bad habit you just kicked. Become a Big Brother or Big Sister. Form new, healthy habits that will broaden your experience and teach you new things.
There's a big world out there waiting to be discovered. Go explore it.