I dont think this has been asked, but i have a question.

If you were really unfit, but you did exercise every day for about a month. Then after that you did next to no exercise for about 2 months, would that bring your fitness level right back down again making the month of exercise a complete waste because you didnt build up on it?
I'm asking because its a simular example to me. I only went on a 2.5 mile bike ride today (where as in the summer i was doing 8-11 miles) and it was the first time in like 3 months that i have been on my bike. It was cold weather though, and my jaw began to hurt after a while (it does in the cold for some reason) and i really didnt enjoy the bike ride like i did in the summer. Anyway i found it quite a bit harder, and i havnt been doing a lot of cardio in between today and my last bike ride. So has that space of time dropped my fitness level a lot?
I weigh about 1 stone lighter to when i did in the summer and i have gained muscle but still it was difficult.
I just feel like im stuck being unfit, i want to be able to do that bike ride without my legs hurting or my heart rate increasing as much.

Any help?

Depends on which aspect of fitness really, and how long you've been doing them. You start to lose muscle due to not using them after only two weeks. But, if you've been doing cardio for years such as bike riding, then take a few months off, once you start back up certain things such as your heart and lungs don't seem to lose much of anything, you're back to where you left off fairly quickly.

But, if you really did only work out for a month, that's really not enough time to make any lasting impression, on much of any aspect. My unprofessional opinion is that you're basically starting from scratch, minus a few pounds, especially in regards to your muscles.

Just keep in mind that riding is harder in the winter anyway, so don't try to compare the way you felt back in the summer with the way you feel now. Even if you stay fit or improve, it will seem harder now.

I know what you're saying, but it's strange reading that, because I purposely try to make my legs hurt and increase my heart rate as much as possible when I ride.

But thats a sign that your body is finding it quite difficult to do the task. When you are fit your body doesnt feel that the bike ride is a challenge.

I'm freaking out a bit, i have a holiday some time in Feb 2007 to Egypt and i want to be thin enough, but im at least a stone overweight and its all on my belly and around the back where your kidneys are.
And now its winter bike riding is really unpleasant. Dont know what to do!

No, it's because a bike "ride" to me is often 6-8 hours long, I'll often ride at 30 mph for long stretches on flat ground, I've climbed 5,500 vertical feet at an altitude of over 10,000 feet. I don't care what your fitness level is... that stuff burns like hell fire. No matter how fit you are, you can always make a bike ride challenging. Watch the faces of the racers of the Tour de France as they cross the finish line. You can tell, without a shadow of a doubt, that their legs hurt like hell, and most of them have wireless heart rate monitors attached to a radio so that all the viewers can see what their heart rate is on TV, and it's sky high at the end. Yet, they're the most fit people in the world. Pain and high heart rates go hand and hand with bike racing.

Your goal for fitness should never be to be able to do a 10 mile bike ride with minimal leg pain and minimal increase of a heart rate. If you truly want to be fit, then once it starts getting easier, you'll just pedal hard and go faster, and the high heart rate and pain will return. Exercise is pain. If it wasn't, it would be called "watching TV" or something.

Ok well i have a lot of work to do then. The cold is so off putting, i prefer the boiling heat in summer, i feel better when its like that. But the cold is horrible, my nose runs and i get an ache in my jaw, and everything is bleak.
Not much to do in the winter really, maybe i should just stick with weight lifting and situps thru the winter to try and get my BMR up, muscle does increase your BMR rate doesnt it?

Yes, after 2 weeks your level of fitness decreases and after a month you really have to work back up. Also, it depends on what type of exercise you were doing. For example, I can run and I am not sore from doing it, but if I ride a bike I get sore.