It sounds as if your problem is that you are applying English phonology (ie: how sounds are organised and patterned in English) to Italian. Are you learning pronunciation passively by ear?
Hereafter, abbreviate L2 for Second Language.
Step 1. Learn IPA.
Why? Only IPA can empower you with:
1.1. independence (because you no longer need to rely on English to conjecture or guess how the L2 word should sound);
1.2. precision (because you know exactly to what sound some book is referring);
1.3. and universality (because you can use this to learn other languages, and to communicate precisely to other people (such as users here) which sound you mean).
For example, Spanish.about.com tries to describe how the letters 'b' and 'v' are pronounced in Spanish below; but its attempt appears ambiguous, and perchance even unhelpful to someone who does not know how 'b' and 'v' are pronounced even in English!
[1.4] The sound of the letters varies, however, depending on the sounds around them. Most of the time, the b and v are what are called voiced fricatives — in this case, a sound somewhat like the English "v" but with the two lips touching instead of the lower lip and upper teeth. Think of it something like the English "b" but quite a bit softer.
Step 2. Read about phonetics.
Why? See 4.2 below.
3. How do you learn IPA and the basics of Phonetics?
See my answer here.
The following quote should explain why even a basic study of phonology pertains to accents.
[4.1] What is phonology? According to Marina Nespor, Italian linguist and author of the book "Fonologia," it is "that branch of grammar that is occupied with the sounds that are systematically used in natural languages for communicating meanings." Put more simply, phonology studies the meanings of the sounds we make when we speak.
[4.2] One important fact to begin with, is the difference between phonology (fonologia) and phonetics (fonetica). Phonetics analyzes all sounds arising from human speech, regardless of the language or meaning. Phonology studies the sounds in context, searching for patterns by determining which sounds contain meaning, then explaining how these sounds are understood by a native speaker. So while phonetics studies how the letter "f" is produced (what parts of the mouth are used and how, in order to say an "f") and how it is perceived, phonology analyzes how the words fa and va have different meanings, despite only differing by one sound.)
