So here is my problem, i do my sit-ups on my bed cause the floor hurts, anyways i put my feet under a small bar of my bed to make doing the excer easier.

Well now i realised i do more than usual so i decided to hold dumbells on my hands to make life more difficult however this never works as my hands end up getting tired of holding them, I also trying doing full crunches,(one were u do normal situp along with the bent kness in air, which u den bring inwards)
However instead of acctualy doing excercise i end up having to stop to breed(i wont be tired from the excercise though)
I also tried doing normal sit-ups on the floor, i must say i found it more difficult however i get the feeling i`m not doing much since i`m not going up all the way(and i`m also told i dont need to go up all the way)

Could you tell me how far i have to go up and wether i`m better off using the bed with the bars or staying on the floor?

You're better forgetting about situps altogether and concentrating on crunches. You should do them on a solid surface and keep your back on the floor as you roll your shoulderblades forward and off the ground. When you get to the top of the movement you should tense your abs so that you feel the burn. You can do them by bringing your knees up if you want but the conventional way is to keep your feet on the floor.
You should try to encorporate some other abdominal exercises into your routine so that you hit them in different ways and target other areas. Other exercises to look into are leg raises, stomach vacuums, reverse crunches, side raises, and winddscreen wipers.

As for the breathing trouble, breath in and out deeply and continuously as you do each rep, holding it for a second whilst you squeeze your abs at the top of the movement. Maybe you are doing too many reps at a time, or going too fast? You shouldn't be doing more than about 20 reps in each set, and if you are then you should look to make it harder on yourself by holding weights. Try holding a weight plate or something heavy behind your head whislt doing crunches - this may be more comfortable for your arms than trying to hold dumbells in each hand.

ive been doing plenty of ab excercises for ages, but i do two in particulary that have really made a different.

The reverse crunch on a declining bench is tough at first but well worth it, and then i also place a dumbell between my feet, lie on my back on a bench and lift my knees into my chest. The first is really helping show the troublesome lower ab area, the 2nd is great for strength. keep doing the rest though, ive just found better results since adding these.

if you are getting tired holding the dumbells in your hand

you should keep it on your chest
basically cross your hands across your chest with the dumbells resting against your chest

if cant do it on the bare floor try doing it on a mat or towel or something
you need to press your low back on the floor during sit-ups this cant be fully achieved on the bed3

@johny100
whats the windscreen wippers

tbh i thought crunch and situps were the same.
Anyways for crunchs, i feel as if i`m not going up enough, hence feel uncomfortable. how far should i go up?
Also i read soemthing about killer crunches? should i do does?

In reply to Benny - windscreen wipers (and I'm sure they have many other names too) are where you lie on your back with your legs raised perpendicular to the floor, and then twist at your pelvis so that they are lowered down to the floor on one side of your body (keeping your upper body as still as possible), and then raise them back up and drop them down to the other side. When done, the movement looks like a set of windscreen wipers. Having never performed this myself I don't know too much about it, but I think they exercise your obliques.

Now to titanium - Situps are different to crunches because the movement comes from your pelvic area, lifting the whole of your upper body off the floor just like if you were "sitting up". Crunches on the other hand, involve just your shoulder blades being raised off the floor, and so what you are doing is rolling your spine forwards. (A good way to test if you are doing it correctly is to pretend that everything below your pecs must stay still during the exercise).

How far should you go up? Simple, as far as you can. Your abs will tighten up the more you roll forwards, and so the more you roll forwards the more effective it will be. Once you get to the point where you can't roll any further, squeeze your abs hard and then relax as you come back down.

How fast should i go? how long should 1 complete one take? Cause im realy finding it difficult to breath while i`m doing them, i end up having to stop for 5secs to breath.

and also is my neck suppose to tense up?

I'd say you should take about 1 second rising up, half a second to tense your abs, and 1 second to go back down. But probably the rising and falling you should do a bit quicker if you can.

The reason your neck is hurting is probably because you are straining it forwards as you lift your shoulders up. You shouldn't roll your head forwards making your chin touch your chest, but instead just keep it still and look upwards. This should stop any tensing that you're doing.

For the correct breathing I think you're supposed to inhale when going up, then hold, then exhale going down.

put them on your stomach or just under your chin. or on your shoulder.