Your instructor's flip attitude concerns me greatly. You don't 'get used to it'. You have to learn proper lifting techniques. It's amazing how much you can lift even with your small frame when done properly. Body mechanics: using your body to obtain a mechanical advantage.
Our class is learning from Brady's Prehospital Emergency Care book and there is a chapter on body mechanics. If your book has one maybe you can practice with a couple of friends?? I know that since we spent those 3 hours in class, I have started to do some squats to strengthen my thighs and some sit-ups to reinforce stomach muscles.
Also, when out on a call, don't be afraid to call for extra manpower when you need to.
Pat