[juancampa]

I actually found a way to do this and it worked really really well.

Find an english song you like and know very well, record yourself singing it, it's gonna sound horrible trust me, listen to it, you're going to notice all the tiny mispronunciations because you know the song very well, and you also know how to pronounce it correctly for the same reason.

Now you have a good reference to work with, pay close attention and start fixing little by little.

It worked for me, maybe because I like playing guitar and signing, but I guess it can be done with other recordings as well, like TV shows or speeches.