I need help with my peekapoo!!!

I have a 1 1/2 year old peekapoo and I could not adore him more but I'm afraid he has seperation issues. When I leave the house he sits by the door and whines and then once he has given up he will go hide under my bed until I get back home. When I walk in the front door he runs up and trys to jump into my arms while whining and just going crazy!! The bad thing is I can't even go check the mail with out him doing this! When I am home he follows me everywhere, including the bathroom. And if I'm laying on my bed or couch it seems that he always has to be cuddling with me. My friends have said that they think I gave him too much attention when he was a puppy. My mom believes his behavior is a result of him having to stay with my aunt for 4-5 months while I was in a job transition/move. I love him sooooo much and enjoy cuddling with him but his behavior right now is not normal and I'm worried!! Some one please help!!!!!