Is there such thing as too many follow-up emails to a professor?
Email is obviously not succeeding, so contact him another way.  Phone, postal mail, visit his office, etc.  You may also contact his department chair and ask if they know of any reason why he wouldn't be answering emails.


  I don't know whether he wants to continue with this project anymore. 


Even if that's the case, you have every right to be told that directly.  Ignoring your emails would not be an appropriate professional way for him to communicate that to you.