First, there is no υ in the word χρειάζομαι.
Second, there are different types of verbs in Greek. Many end with ω, but not all. χρειαζομαι falls into the category that end -ομαι. It's just the way the language works. It conjugates like this: εγώ χρειάζομαι εσύ χρειάζεσαι αυτός/αυτή/αυτό χρειάζεται εμείς χρειαζόμαστε εσείς χρειάζεστε αυτοί/αυτά χρειάζονται
Thanks for the reply. I could read the explanation in the tip notes just a minute after having sent my question but I hadn't realised that I was writing the verb incorrectly, thanks for letting me know.