I felt that way, especially as I was changing my name. My old name became unknown, strange to me...like I was using a totally random person's name...(Like if you wrote, "Hi, my name is Ralph Smith" and felt no connection to "that name" and "yourself", that was me)
Same thing with old pics...I almost feel like someone should say, "That's your cousin, who you never met. But he looked just like you did back then..."
For me, it's both painful and a relief. Painful, because that "part" of me is no longer part of me; and a relief because that "part" of me is no longer a part of me.