DO NOT TRUST YOUR EAR!

Do not trust your ear when learning a foreign language. All we hear is not decoded properly all the time.
The ear sends the sound to the brain and the brain decodes it... with the information it has in stock about sounds, which belong to its mother tongue!
So, do not think that what you hear is the right sound. Ask your teacher.
Of all the skills in language-learning, sound is the most important and difficult to acquire.
Language is sound! Never forget.
My PHONÉTICA INGLESA PARA TORPES, compares the sounds of English and Spanish and can help you improve both languages. Do yourself a favor and study it: it is simple and easy to understand.