Does an IV need to be used in AES CTR mode? If I encrypt a message once using AES CTR, will I need an IV? Additionally, if I do use an IV, will I need to send it with the cipher text?
Yes, you need an IV in CTR mode and you do need to send it with the ciphertext, or at least make it possible for the encryption process to know it. Specifically, you need a nonce. The nonce can be anything, as long as it is unique so no key:nonce tuple ever repeats. The nonce is part of the counter. CTR mode operates by encrypting this value and XORing the result with the plaintext. When the next block is to be encrypted, the value is incremented by one and the process repeats.