Hmmm, not sure what to say. I would say if you are really concerned about it I would go see a doctor. My best guess is that your metabolism slowed down but I am not a doctor =/ It could also have something to do with affect. Like when you are sad you tend to eat more but not realize it. Also the weather could have something to do with it....but not really this time. Like I said, I would go see a doctor.
The other thing that would help out is keeping track of the calories your take in and the ones you burn. I can not stress how much this has helped me out. For those with smart phone I have an app (droid network) called Calorie Counter by Fatsecret and I love it. It has a lot of resturants in there with the calories and also a barcode scanner that will tell you how many calories, fat, ect in most products. It also gives you an estimate on how many calories you should eat per day based on height, weight, sex, and how active you are. The one thing that I really like about it is that it also has a calorie counter for exercises and includes daily activities such as sleeping, sitting, standing. And it also gives you low calorie recipies. Serriously though, if you have a smart phone get this app or something like it. If you are like me you have your phone on you everwhere so you can enter the meal you ate as you finish it.
With a calorie counter just keep track of both calories in (eaten) and out (exercise) and as long as calories out is greater than calories in you will lose weight. How big of a difference there is will determine how fast you lose that weight. It takes about a 3,000 deficit to lose a pound. I have been trying to burn between 500-1000 calories more than I take in each day meaning I will lose about a pound to two pounds a week which is considered healthy. If you want to lose more than that in a week I would suggest talking to a doctor first.
Also, and this may be important to you sushisoap, weight training increases your metabolism. When you lift weights you get mirco tares in your muscles and repairing them burns calories. It takes a long time to repair them too so your muscles are still burning calories hours after you are done working out. Squats, lunges, sit ups, push ups, all of these can be done without weights or any equipment. Squats by far are some of the most effective workout since it works most of your body.
As for food, nothing is bad for you as long as it is eaten in modertation. I have eaten fast food at least once a week for the past few weeks and I have lost five pounds. Don't force yourself to give up anything, it is actually harder and you are more likely to fail than if you eat it in smaller portions or substitue something else. Like say if you want sweet stuff instead of candy I have been eating watermelon (I am on a huge kick right now, I LOVE IT). It fufils my need for sweet foods. But saying you aren't going to eat candy will only make you think of it more and thus make you crave it more (its been a while but I did write a paper on this in college). If you insist on cutting something out of your diet it is best to do it in moderation. Take soda for example, if you normally drink 5 cans in a day go down to 4, and after two week or a month or so go down to 3 and so on and so forth. OR replace it with something else, coffee or tea (coffee is fine, it only becomes bad when cream and sugar are added, same with tea). I love my tea but I don't drink it enough. Make a big batch and keep in in the fridge so you can have it hot or cold.
Sorry for such a long post, I am kinda bored at work =/ Also sorry for any spelling mistakes (I've always been bad and this computer doesn't have spell check in the browser).