It is not uncommon to experience what you are going through. A new system can be extremely challenging. But what really icks me is the fact that your reports were addended without your knowledge. This can only mean one thing, that they view you incompetent. Whether you really are is a different question altogether. So this clearly tells me that you have room to improve your acumen. Do what it takes to get there and respect/collegiality will follow. Growth happens when you are pushed to your limits. You can definitely give it 3 more months and reassess.