Very simply when they are new born their digestive system is fragile and needs time to build up good flora. I am not surprised it refused the second pinky at its second meal because the first meal was probably just too much for it. Feeding two prey items right away is absolutely NOT a good idea.
Start with one small pinky and do this for 4-6 regular feeds and then move up a bit if the animal is growing well.
Also I would reccomend not handling it alot either while it is still a newborn, nor doing the feeding from hand trick. Yes, you will get it to work some but it creates an instable atmosphere for hte animal to learn from. Just put the mouse in a container and put the snake in and give is some peace. In the first 3 months, you need to focus more on getting the snake used to its surroundings and feeding patterns, and not spend much time trying to socialize it till it has grown a bit more.