I have a brummy lilt and my friend who studies linguistics has pointed out that when I say 'i' (as in high) it sounds a bit like oi (as in loit). I find it almost physically impossible to change the way I am saying this. i am wondering if anybody knew what the physical mechanics for proper pronunciation for this vowel was.

I am also told that when I say 'a' (as in ray) it sounds a bit like 'I' as I already pronounce it. 'ee' (as in tweet) also sounds more like 'ay', for example university will often sound universitay.

The alphabet when I speak it sounds a bit like: oi, bay, say, day, ay, etc. rather than A, B, C, D, etc.

People often have a hard time understanding me (especially foreigners) because my accent is so thick so it is not as if I am just trying to adjust my voice out of self-consciousness or anything. If people could understand me I wouldn't mind.