Dramatic Weight Gain?

I weigh roughly 210 pounds and am 5'10". I'm trying to lose some weight for the summer season, and have been counting my calories and doing more cardio than usual to achieve this. I'm using the Dailyburn app for the iPod, and I eat about 2200 calories a day, although it says I can eat up to 2800 and still lose weight.

I was weighing myself every few days, and watched as it gradually decreased. 209, 208, 207, etc. After about two weeks I was down to roughly 204. I was perfectly happy.

I've had a relaxing weekend, but still didn't eat much. For the past two days I've averaged about 2800 calories, and the only exercise I've done is playing at a playground with my little cousin today. I weighed myself last night, and was 208. I had just eaten dinner, and I was frequent to weight changes of a couple pounds daily, so this didn't bother me too much. I weighed myself just now, and now I weigh 214. This is an all-time high weight for me. I really have no idea what's going on, and am kind of upset. I also noticed while taking a shower that I have a decreased range of motion in my arms. Help?