I Recently Had Surgery To Replace My Knee. Since That

I recently had surgery to replace my knee. Since that operation it seems that I get dizzy especially during a shower. I also feel very fatigued and it is hard to raise my arms or hold my head up. i don't know if it is chest congestion or what it could be. i have had a couple of occasions when i cough up flem i feel like i am about to pass out, it felt like the lights were going out.