If your H1B was picked and your OTP expired in September, then don't worry, there's something called "Cap-Gap Extention." This extension keeps you in the United States, legally employed, and waiting for the processing of your H1B. The Cap-Gap would apply automatically if your employer filed a petition for H1B before your OPT expired.
H4 EAD: Work Rights or Loopholes?
You must contact the international student office at your University to verify that your SEVIS record has been updated. They may provide you with an updated I-20 form that includes the extension of work authorization under Cap-Gap, which you may need to demonstrate legal status if required.
On the other hand, if your H1B is denied, then the extension comes to an end immediately. You will have to stop working and leave the U.S. or try out other visa options. It will therefore be good for you to keep yourself prepared with some backup in mind in case everything doesn't fall in place as expected.