Everybody's anatomy is different, and some cervices are *right there* and others you have to hunt for. Warm hands and going slowly do help.
Does your hospital have, for lack of a better way of putting it a 'vagina in a box' that you can practice on? (I've heard other, less polite terms too, but will stick with this one.) That helps too.
It is one of those things like starting an IV - the more you do it the better you'll get at it. I'm no expert here and there are others who will come along with better advice, I'm sure. But if you've only done 3, please don't beat yourself up! You're just starting out! It will come, and it might just click one day and no more worries.
If it makes you feel any better for the moment, everybody has had trouble, and sometimes even the docs (sometimes especially
the docs) can't figure out what everything is in there.