Is there a way to convert my ebook to an audiobook

no

There's a neat little app called "Lips" that reads aloud and makes an MP3 of it. Of course, like nearly ALL read aloud apps, it has trouble with some punctuations and pronunciations, but it IS free.

http://mac.softpedia.com/get/Audio/Lips.shtml

You can use audiobook creator (http://codingday.com/mac-apps/audiobook-creator/) which is on the App Store to convert drm-free ebook to audiobooks

Depending on where you get you're books they may not be drm-free though.