Lost ROM after therapy session

Hi I am 39 yrs old and had my first TKR on my left knee this Nov. 2008. I have had nothing but trouble and alot of pain after this surgery, after surgery my knee froze up and I had to have a manipulation under anesthesia done just a month after the surgery.
I thought finally was getting some progress was starting to finally have good ROM was up to 118 then on Dec 30, Tues I went to therapy which my normal therapist was on vacation so had another therapist work on me of course i went through the torture walked out in tears, that night I felt something was wrong with my knee I felt tightness and swelling and my knee was not bending as far as it was used too, plus I started having sharp pains in a location I never had before and I started getting the chills.
The next day I had another session scheduled which i did attend I mentioned my concerns and of course my ROM dropped from 118 to 100 in one day, and all she kept telling me was that she didn't think it was from the session just that my knee was reacting to being overworked. She did take it easy on me that day cause again I was having chills and in a lot of pain.
I was scheduled for therapy again today but canceled,because I am concerned i am still getting chills my knee is stiff swollen and hardly bending at all, feels like it is freezing up again, please some advice would be helpful?