[Q] New to ROMs, need help fixing my phone. topic

Hi,

So I flashed CM12 to my phone - the most recent nightly. All was good except it wasn't recognizing the SIM. So I asked in reddit and was told it was a new issue and to flash back to the 18th. My computer no longer recognizes my phone being plugged into it via USB, so I just directly downloaded it, booted into recovery, and flashed the version from the 18th.

Now my phone is stuck on an endless boot animation of the little blue alien and won't boot up. Any next steps would be greatly appreciated!

Thanks.