Number 1... DON'T panic.
Number 2... >230 is very good, don't be down on yourself if you get lower than that (as you will have plenty of opportunities to offset that short-coming during your clinical rotations), but by all means... it's not impossible.
I don't know how much time you have, but if you can take 4-6 months off to prep, I feel that would be a wise decision in your case.
Resources you should use:
1) For overall topics you need UWorld and Goljan's Rapid Review Pathology. Limit yourself to these topics until you feel you have completely exhausted them.
2) Most exams have an abstract element of biochemistry. It's important to have an understanding of metabolism, inborn errors of metabolism, enzymes, agonists/antagonists, etc.; Do not try to read and remember, it's extremely inefficient and ineffective. Get the 'DOCTORS NOTES Medical Biochemistry poster,' and use that for all your biochem studying (it's laminated so you can add any notes you come across in UWorld/Goljan to it and have a nice visual picture of biochemistry in its entirety by the time you're ready for your exam).
*Note, the USMLE is a very, very fair exam. But, you will do bad if you simply try to remember answers. When you're studying, make sure you take the time to understand why something happens because questions are made to see if you can take information you've learned and apply it to a situation you've never seen. This was my problem with First Aid and why I stopped using it and why I would not recommend it to anybody... It is abstract memorization, which is NOT helpful.
** Note as well, I was very neurotic with my studies, I used all those above, plus pathoma, kaplan, several qbanks, several rapid review books, and pharmacology and pathology text books, and first aid. When I finished the exam, all I thought to myself was, "Wow, that was easier than I thought. I should have just used more UWorld/Goljan/DoctorsNotes." Because literally everything I was able to know and recall on the exam was from those resources.