I was speaking to someone a few days ago. I was referring to someone else (a male) and realized something in my speaking. I was amazed that I had never noticed this in my speech before. Now it is bugging me and I try to listen for it in others' speech, but I never am listening for it at the right time.

What I was saying was something like "I gave it to him". But I realized that what I actually said was more like "I gave it to'eem". I had never noticed that I changed the pronunciation of the word "him" to "eem" in some cases. I quickly realized that I was dropping the "h" (of course), and saying the sound "eem" to differentiate that word from the "oo" sound in the word "to".

It has bothered me since, although I know it shouldn't. It must be pretty common, since no one else has ever drawn my attention to it. I just wonder how many other examples there are like that. The obvious proper one is using the "schwa" sound when saying the word "a" before a word beginning with a consonant sound, and using "an" before a word beginning with a vowel sound (but not necessarily a vowel, of course).
(Incidentally, I am from southeastern USA.)