Hi Mayge,
Firstly glad to hear you have recovered from your injury and are back playing again! To me it sounds like it could be one of 2 problems or a combination of them. As you said after the injury you started to play really well but had no expectations. Once you start to play well you expect to be that level all the time and when you aren’t it can be frustrating. So try not to stress or worry and understand you will always go through ups and downs and improvement takes time.
The 2nd is your training, and are you practicing correctly? It’s It important that you focus on areas you want to improve with specific exercises. You also need to make sure your aware of what your mistakes are, have you tried video recording yourself? Let me know and also what seems to be getting worse. Tom