There are several possibilities:

If you are gaining weight AND getting smaller, then you are gaining muscle, not fat, and this is not a problem. In fact, you should celebrate!

If you are gaining weight and your clothes are getting snugger instead of looser then you might need to tinker a bit with your diet, you don't need to resort to extreme measures (more later).

If you feel you can't avoid the unhealthy eating habits you might need to get support for an eating disorder (with which I have no experience and can't make any recommendation). There is an ED community here if you think that will be helpful.

Tinkering: for best results, consult a nutritionist. S/he can help you find the proper food balance to support your current level of activity and maintain a healthy level of bodyfat.

Having said that - when I am biking a lot I eat more carbs. Some of those carbs live around my middle and STAY there. Apparently the body thinks it needs to hang on to fat if you overstimulate the metabolism... so one possibility is you might need a few more rest days or slightly decrease the intensity of your cardio workouts. OR you might need to adjust the amount or kind of carbs you are eating.

A helpful tool is to keep a diary of everything you eat. Using a reference like Netzer's Food Counts you can calculate how many grams of carbs you are eating. Change that level consistently for a week and weigh and measure yourself at the end of the week. That should tell you whether you are getting the result you want.

The one thing you should not do is weigh yourself daily. You'll find that weight fluctuates up and down throughout the day and throughout the week. Too easy to obsess over the number - and that number is meaningless without body measurements.

this is of course assuming that you are eating enough protein to sustain the muscle you have. It is possible if you are only doing cardio when you workout that you are losing some of your muscle mass. do you do any lifting?

I also do pilates which uses your own body weight to build muscle and I do leg exercises on weight machines but nothing with arms(except pilates) or chest because I get chest pain and if i work out my chest its hard to tell the difference between the chest being sore and chest pain...

I do cardio everyday but I only do the eliptical or the treadmill for 2 miles a day and I am walking not running. I get toooo out of breath if I do anything but walk and so my doctor has been recommending for months for me to walk.

as far as measurements... I have lost and inch on my hips but nothing anywhere else.

In that case I wouldn't worry too hard about the number on the scale. Muscle is denser than fat, which means it takes up less space and weighs more.

If you are losing inches, then you are building muscle. This is good news because it means you are increasing your ability to metabolize body fat. It's healthy pounds.

The scale only tells you how much you weigh, not what your body composition is. The lost inch from your hips is a much better indicator that you are making progress. Congratulations!

As you continue to exercise and eat properly you may notice that some fat deposits don't change at the same rate as others. Your body decides where it comes off first - it's not something you can control. As long as some measurement is decreasing you are making progress.

In fact, you might even retire your scale for the next few months and just chart your progress with the tape measure!

Might I also compliment you on your perseverance with your training and listening to your body - you'd be surprised how many people do themselves a mischief by ignoring the signals their body sends them!

I have exactly the same problem at the moment & the best answer I can come up with is just to stop standing on the scales. I find that if I get on them to find that I've gained weight it demotivates me.

Keep doing what you're doing & concentrate on being fit & healthy.

never judge by the scales judge by the way your clothes fit you. Also muscle weighs heavier than fat

i'm the same way, but sometimes it's just like that. Keep working out, and keep eatting good food. You will loose waight. I know it's easy to say i'm not going to eat or i'm going to take diet pills or i'm going to not keep my food down. BUT YOU HAVE TOO. Be heathy and you will be so much better 4 it :)

Fat takes up more space than muscle.
Muscle is a good thing, even if it weighs more.
I think the biggest mistake that people make is to rely on those numbers on the scale.
Your clothes don't lie, so when you go from a size 15 to a 9, but have lost only a few lbs, would you be upset?
You want to gain the muscle because it helps you burn even more fat.

Throw your scale out the window and go by you clothes.

when I first started working out it was because my Dr. had been trying to get me to lose weight for a long time and everytime I told him i could but it never happend untill, the day he said I couldn't do it! and he wouldn't beleive it untill he seen it.I seen him 3 months later 40 pounds lighter!he said keep it up 3 more months i was down to 183 pounds. then he says don't lose any more that i should weigh 190 for my height. I didn't listen and just kept pumping the iron before i knew it i was 207! I thought 207! whats going on? My pants we tighter in the legs mainly so i stoped working out for awhile and went down to 194 in a couple months. I was starting to lose all of my mucle mass now. not hte best thing to do, so keep working out and keep building that muscle!

when I first started working out it was because my Dr. had been trying to get me to lose weight for a long time and everytime I told him i could but it never happend untill, the day he said I couldn't do it! and he wouldn't beleive it untill he seen it.I seen him 3 months later 40 pounds lighter!he said keep it up 3 more months i was down to 183 pounds. then he says don't lose any more that i should weigh 190 for my height. I didn't listen and just kept pumping the iron before i knew it i was 207! I thought 207! whats going on? My pants we tighter in the legs mainly so i stoped working out for awhile and went down to 194 in a couple months. I was starting to lose all of my mucle mass now. not the best thing to do, so keep working out and keep building that muscle!