PLEASE read everything Jenna said thoroughly about 5 times! A closed adoption means that the record are sealed and neither mother nor child are ever to know each other (or anything much about each other) or meet. At the least until the child is an adult and sometimes never.
Access when the child is of age varies depending on where the adoption occurred. Check in your province as to laws there. Laws are constantly changing too, as many feel open records are not fair to adopted people.
As Jenna says though, your child may still find you someday though even if the records are sealed. My son found me when he was nearly 32. It was legal in the state his adoption occured for a intermediary to search for me. I do not believe a woman has a right to remain anonymous from her child.
Think not of what is best for you, but, your child. I would not recommend a closed adoption to almost anyone. Also check out Heather Lowe's new blog on crisis pregnancy. She is continuing to add some very helpful info there daily and can give you much to consider.
http://www.adoptionblogs.com
Click on "crisis pregnancy" on the right hand side.