Even though your preceptor doesn't always work the same shifts as you, she should be sitting you down once a week or so to have conversations about your progress. She should also be asking you what areas you feel are your strengths and weaknesses at this time. I suggest that you contact your preceptor and schedule some time (soon) to come up with a tentative plan and/or have an informal chat about your progress.
Your unit should also have an orientation coordinator and/or nurse educator. This is the person that you should go to if you talk to your preceptor but things are not working out (ie. he or she doesn't seem interested in teaching, your personalities don't mesh, etc).
Finally, if you are still not making any headway I suggest speaking with your nurse manager. A good manager will try to make it out onto the floor periodically to spend some time with her staff. However, the reality is that in the fast-paced world of health care the manager may not have the time to do this as frequently as she should due to other responsibilities. Some managers are also not as committed as others to communication with their staff members, as sad as that may be...
If you are really running into problems, then I suggest that you conduct all of your communications in writing (ie. by e-mail). This way if your orientation period finishes and your manager feels that you did not make the necessary progress, you will have some evidence to show her that you have been making a good-faith effort towards getting the kind of training that you need as a new graduate.
Worst case scenario, human resources will get involved in this process. Having evidence in writing of your attempts to contact your preceptor, orientation coordinator and manager will show that you are holding up your end of the bargain. This might allow you to request a transfer to another unit or to get an "eligible for rehire" letter should you choose to leave your unit.
Finally, you should be bring your orientation checklist to each preceptor at the end of your shift and make sure that they are checking you off on all of the competencies that you have accomplished. If you partially completed an item on the list, have them make a notation in the margin. Without a consistent preceptor, it can be very difficult to complete these lists unless you are very diligent about it.
Good luck

We were all new grads at one time and we made it through. You will, too!
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