I have a 22 month old who is like this too. He's been with me for three months as well and still cries when I go out of his sight for a moment and often cries briefly at drop-off and pick-up. He has separation anxiety and clings to his mom a lot at home too, so it is not out of character for him. He has fun while with me and is a very happy kid, but just needs to be nearby all the time (he follows me into the bathroom when I take diapers in there etc.). I encourage him to go and play rather than hanging around me at the park etc, and usually he will, but at least I know he won't run off...looking on the bright side! I figure he will outgrow it eventually, but is is part of his personality.