Hi Andrea. First, when we read poetry we tend to speak more artfully, and less naturally, especially in rhythm (as James pointed out). So it's not easy to get a full sense of your pronunciation in regular conversation. Here are some patterns I noticed:
Where a native speaker would use the weak form of a vowel, you tend to use a strong vowel (for example, "this" should have the vowel sound of "is," but sounds more like "these").
The "th" should be aspirated, but here it tends to sound like a "d".
The number of syllables and syllable stress within a word: for example, "imagine" should be three clear syllables, with the stress on the second syllable, but here it sounds more like two syllables (something like "made him"). "Near" should be one syllable, but here it is pronounced as two.
When you form the R, your tongue should never touch the roof of your mouth (as is typical of Italian and Spanish): outside of unique regional dialects, the English R it is mostly a rounding of the lips, with the tongue retracted.
Patterns of assimilation are lacking: this is where two sounds come together (usually where two words meet) and the sounds change. For example, when speaking at a natural pace, the final "t" in "thought fox" will be replaced by a brief interval of silence (this usually happens when a hard consonant is followed by another consonant). Also: unvoiced consonants (t, s) often become voiced (d, z) when they follow a voiced sound (such as any vowel, or an M, etc.).
Some of these pronunciation issues are more cosmetic (you can be understood, and it just sounds like an accent), but others are more problematic because they can create listener confusion.
I hope you find these suggestions helpful!