This person keeps signing me up for a very specific topic with email newsletters and websites and is there anyway to find out which IP address this is coming from when they sign me up on these websites?

It may not be a person it may be different websites you go to you leave behind tracking cookies. In return you start getting all kinds of spam from websites you have never even heard of. You can block the emails but do not ever open them to unsubscribe to them that will only verifies your email address and you will get a lot more. Hope this helps!!!