Drakejake,
Bad4u is dead center.
I found that I had the same trouble with the smaller guns. With a smaller grip and a DA trigger, most people have a tendency to stick their trigger finger further into the trigger guard. This is partially because the smaller grip/trigger dimension, but is also because there is a tendency to use a lower (stronger) part of the finger to pull the stiffer trigger. Granted, this is not true for everyone, but for many people, it will cause you to shoot low and left (if right handed).
On all of my full-size guns (double or single action), my trigger finger contacts the trigger about halfway between the end joint (knuckle) and the tip of the finger (sometimes called the middle f the pad). However, when I shoot a smaller gun (say a Sig P239 or a Ruger SP101), I find that (if I'm not paying attention) the trigger will rest right in that first joint or even below it and I'll hit low and left. If I catch myself and reposition my finger, I'll shoot better. If you get into, or below, that first joint, the natural muscle and joint action of the trigger finger will change your POI.
You can try dry firing with different finger/trigger contact points and you'll see what I mean. No matter where the trigger contacts the finger, dry firing helps build up the finger muscle, so dry firing is always a good idea! Hope this helps.