Stop fighting an uphill battle and run with open arms into the land of shoulder rests and chin rests! Beware that you could definitely get lost : ) There is a huge variety of these contraptions on the market. One thing to keep in mind: you need to try them out before you buy them!!! Just like buying an instrument, you DO NOT want to buy it until you try it. Its like a marriage, you're going to have to deal with this set up for a LONG time and you need to know what you're in for.
Just because one thing works for me, does not in anyway mean that is will work for you. I prefer the Bonmusica Shoulder rest and the Wittner hypo allergenic side mount chin rest. Personally, I like to go with my students to pick these out to ensure they get the correct things. We always go to a shop where they are very helpful and accommodating. Here in Philly, we go see David Michie's Violin Shop on Locust St. (downtown). He is amazing. (He's not paying me to say this lol, its just true). He has a wide variety and is very knowledgeable about this.
Important things to think about:
Everything needs to be tried out with correct posture (shoulders back, head straight ahead, chest high etc.)
The instrument should be able to sit on your shoulder with the head gently resting on the chin rest. (do not stray from a natural posture, no twisting the neck, shoulder, or back into weird positions.
Can you hold the instrument without the help of the arms?
Can you move the arms around with ease?
Can you breathe easily?
Is the scroll eye level (i.e. NOT pointing down)
What angle is the instrument at? Is it sitting in the center, way off the to side, or somewhere in between? (also, notice here if the left shoulder is raising or hunching in to support the instrument. You don't want this) Somewhere in between in best, but you should be able to move the instrument around left or right, if you need.
Is there any tension in the neck especially? Can you see the muscles and tendons tensing up in the neck?
Is your chin on the tail piece or on the chin rest or both? You do not want it resting on the tail piece, this alters the pitch of the strings and effects the vibrations of the instrument.
That's about it. Can you see why you might need help? If you can't go with your teacher--make sure you call around and get a reference (preferably from your local music school or conservatory).
Good luck with the search. It's worth it and just like finding the right partner, you'll be really happy when you find the right one.