Welcome. There is help here. Make sure you don't use your real name or your child's real name, so if you ever need to, you can vent and know your child's school, doctors, relatives or whoever cannot get offended because they won't know it's YOU.
Do a sig when you can, like mine below. It keeps the information straight so you don't have to repeat yourself with every post.
The Connors test is useful, but it's only a starting point. ADHD is fairly common but there are a lot of other things that can look like it. Similarly, ODD is something you might observe but it needn't be the bad news with no cure that doctors seem to enjoy torturing parents with. Generally, a number of conditions (including ADHD) can also produce, in a child who is feeling unheard, frustrated and who is not coping, the signs that can be indistinguishable from ODD. If you treat the underlying condition and make other changes in how you handle the child, the ODD-like effects can rapidly ease.
Read what you can on this site, there are some great posts in the archives too. Other parents have been where you are now and found a lot of ways to help their child. Learn from their experience.
Another book to read - The Explosive Child by Ross Greene. It gives some different approaches to help with the ODD-like problems, regardless of what the underlying condition might be. Google it, there are some sample chapters out there which should ring bells with you. Also on the Early Childhood forum there is some discussion on how to adapt the book for younger kids. Read that too, it could give you some advance insight into the book. If you're reluctant to buy yet another book, try and find a library copy. It will help. It is not a cure, though.
You describe your son as a beautiful boy - so there is something about him that is loveable. He's not being a bully, but is a problem at school - exactly what are the problem behaviours? It could help us to know.
Something else I suggest - listen to him and let him know that you want to hear what he has to say. He says he hates school - try to find out why. He's entitled to his opinion, chances are if you were in his shoes you'd say that school is torture too.
But school shouldn't be torture - why is it? What is going on there that upsets him so much? And is there anything you can do, to ease the pain for him?
Once you have an official diagnosis, then you can put some measures in place for him, such as an IEP.
For now, keep a diary on him and write down your observations, your issues, any specific problems that are happening. Keep this up, you need to do tis for years. But it is worth the effort because as you read back over old entries, you will see that he is making progress. Sometimes you can pick up patterns of past problems and use this to advantage.
Written communication between yourself and the school is also a really good idea because it helps both you and the teacher stay on top of any issues. Again, either of you can see patterns. It was this sort of communication re difficult child 3 that helped me and his teacher see a pattern in his behaviour - when he was coming down with a cold, his behaviour would be a lot worse in the three days or so BEFORE symptoms showed up. Once he had the cold - his behaviour was much better. Then again as he was recovering, his behaviour would be bad again. So knowing this, we often chose to keep him home for an extra day or so, until he was coping again with the changes in his body due to the illness recovery.
A kid who hates school isn't necessarily a kid who is a bad scholar. Sometimes a bright kid can be bored, then misbehave. Or some topics might be challenging for him and a bit of coaching in those subjects can help.
What you need right now is information, a broader picture on what is actually going on from his point of view, and a diagnosis that you can use for now to get things happening for him.
He will get there. Sometimes just knowing it's not his fault, can make a difference to his behaviour.
Marg