Going to the gym but gaining weight?

I'm trying to slim down and I have been going to the gym around 5 days a week for about 3 weeks now. I used to work out a lot and I was in good shape, but that was a while go. While there I usually jog for 5 minutes at 5.5mph and then do sprints of 1 minute on 30 seconds off 5 times. After that I will do an ab circuit and then do weight training using both the machines and free weights. I'm 5'6, started around 155 pounds and trying to get down to around 130 lbs. I eat generally pretty healthy and log everything I eat using a scale so I know the nutrition I get every day. I've usually been someone who can lose weight really easily, but now I can't seem to lose weight, in fact im now almost 160. I took my measurements a week ago, but havent measured myself yet. I'm not sure if I feel like I look slimmer or not because in the morning I feel like maybe a little, but by the evening I look swollen and flabby. I would like to do more cardio, but I have knee complications that inhibits that. I'm hoping that as I get a little stronger my knee will too and I can go for longer. Is there any reason as to why I keep gaining weight? I switch up my workouts so its not like I just keep doing the same things. The only thing I can think of is water retention, but 4 pounds of it? If anyone has any advice please let me know!