It's been almost a year since I got my ACL surgery (August). My recovery time was great, by 6 months I was weight training again and by 8 months I got a PR on my squat. Around this time, my knee felt great and I had no problems or hesitations when doing any physical activity. 

I play soccer in HS, and am also a soccer referee. I reffed a ton of soccer games this april/may and played in pick-up games and practiced with a team. This activity was not a problem for my knee.

So now in june, I trained one week with my team (4 days of workouts) and I felt fine after that. On sunday the same week, I reffed some soccer games and I could tell that my knee was swelling. The day after, I woke up with a sharp knee pain, as if i was 1 week post op. 

Since this, I have stopped practicing soccer and tried to ice my knee to reduce the swelling. Icing and Aleve did not help that well. 

3 weeks later, there is little to no improvement. I can tell that there is still fluid in my knee. Whenever I try to flex my thigh muscles, I can only feel tightness and pain in my knee. I believe I overworked my knee. But what confuses me is why it has not healed yet. I have done heavy lifting and a lot of running prior tp this incident and it has felt fine.

What are the possibilities of why this is happening? Should I consult my doctor? What can I do!