hi, congratulations on starting your phd :-)
Don't worry, the first year can be worrying especially when you feel that not much is done.
Issues with collaborators are common in most phds.
Since you are working in a different field now, it is understandable that you feel more anxious and confused at times. This is normal for most people, don't let it discourage you. Switching fields takes time, some people transform like chameleons, some need more time, some cannot adapt at all. You need to give yourself more time.
You also need to take care of yourself. Sometimes you need a break away from your phd work, take short walks, spend time with friends, talk to family, go window-shopping, exercise, do something.
Also, when you are able to concentrate, focus on your new topic of study. Since it is completely new to you, it should also be fun and interesting to learn, why not :-). Focus yourself on this instead of dwelling on your insecurities. The insecurity feelings will always be there, but these come and go.
Choose to be happy, and think positive.
Remember that if you feel lost, you can be found again.
Take care
love
satchi