I have type 2 diabetes and take Lantus and Apidra insulin. I am eating healthy but continue to gain

I now weigh 222 lbs.  This is so discouraging since I am trying so hard to lose weight.  Can you tell me why I can't lose.  I am not able to exercise very much.  I ride an exercise bike.  I had both knees replaced in Sept. with the Oxford knee replacements and did not do well from this surgery.  My doctor can not tell me why I did not do well--he just says he doesn't know and basically blows me off.  I was in pain prior to my surgery but now basically I can just barely walk.  I am very discouraged and the harder I work to get better it appears that I continue to not improve.  I feel if I could lose some weight, I might have a chance with my knees improving.  Can you help me with some ideas?