Hi starblue,
For a start, there are many level of friends, but from what I see in your post, "your ex" seems to treat you more than a normal level of friendship, he wanted to be there when you needed it most. You can't stop him from having feeling for you unless he choose to move on. Or maybe he is just doing it as helping a friend in need.
Some actually find it had to maintain a friendship after a breakup because they may still have feeling for one another but they don't want to lead each on.
The main thing is, if you have already move on and just treated him like a friend, just tell him that he is just a close friend whom you can share your problems and troubles with, but clarify that you both cannot be back together because both of your characters just don't match and you will always treat him as a friend.
All the best.
