Hi and welcome to the board!
First of all, hugs. Glad you found us, but sorry you had to.
My daughter is 6, and currently diagnosis (diagnosed) as ADHD/ODD and possibly bipolar, so I know what you are going through. Life is very unpredictable.
The good news is that you are light years ahead of many, having dealt with your son's issues head on when he was young. That is commendable. The bad news is, so much of it is trial and error. And while one medication works great this month, next month it can wreak havoc.
One glimmer of hope that I can offer is that my daughter had problems in daycare too, but once she started school, she really was fine. In school. She saved it all for me, but she did great in school her K year.
Might I suggest you get yourself a copy of "the explosive child" by Ross Greene. Very good read, has great ideas about dealing with these difficult children.
There are many more wise warrior moms who will be along to offer their advice and experience shortly. Share as often as you need to, do not be shy. Again, welcome!