Now my son very attached to pacifier. He cries when i took it especially when he bored or sleepy. So worry about it.. is it ok to let him use it for prolonged time?

If he only uses it when he is sleepy, it should be fine. My boy used to be very attached to the pacifier but we only allow him to have it when he is sleepy. Other time, we don't give it to him at all. If he is teething, we give teether instead, distraction is the best thing to do.