weatherized bedroom

Our master bedroom is located in front of the house with 4 windows. It is unbearable during the winter season. The temperature difference is significant to the point that we close the door so the rest of the house does not get affected. We have been putting off trying to fix it since we are not sure where to go. I been reading about energy audit? Can someone recommend someone or company that can find the source of the draft/leak? or find measures to insulating the room better? Thanks in advance.