two good pronunciation websites

Many people failed SEP. So English can be an issue.

http://www.uiowa.edu/~acadtech/phonetics/#

http://www.howjsay.com/

These two websites are good for self-learning.

There are many accent reduction services that can be googled. They charge big bucks but may not worth it for you. There is no general rule for everyone. Speech pathologists need to develop a treatment plan on a case-by-case basis.