My house is so quiet and boring and he is surrounded by things that he cannot touch- it is no wonder he wants to stay there sometimes (he is 13 months, but this did not just begin!) Just wait until the opposite is true and he does not want to leave your side. A little boy at the day care is 2.5 years old and he wails and screams when his mama leaves him.
Your son loves you, and you are 100% not being replaced. You should be happy that he likes the place- that is a good indication that they are making him feel loved and protected. =)