l can not go up all the way when l do sit ups or crunches. And can not do pull ups or anything!!! Help please!?

start off doin small push ups which is when u rest on your knees and lower yourself down and push up with arms or do sit ups half way and then back down whcih at a later stage of doing this you should be strong enough to do full push ups/sit up etc

Use small weights, and use them. then gradually use bigger, heavier ones.

For the first one you do, try using a can of beans or something. Do that for a while and it helps tone your body. Then move onto the bigger, heavier ones.
xx

For Push-Ups:
Try laying on ur belly, then do a push-up, but with ur knees still on the ground. For example, u r only pushing up the weight of ur upper body (instead of ur whole body), because ur knees r on the ground & r supporting ur lower body weight. Do these 10 times, 3 times a day, 5 times a week.
For Sit-Ups:
Sit in the upward position of a sit-up (not in the laying on ur back position) with ur bottom about a foot away from a wall (face away from the wall). Now do a sit up, but only lower ur back until it touches the wall. This way, ur sit up is only going from the 90 degree upright position to about the 45 degree half-way down position, instead of all the way down to the floor. Do these 10 times, 3 times a day, 5 times a week.
For Pull-Ups:
Instead of doing a full pull-up, find somewhere where u can hang (like the pull-up bar in Gym Class) & just work on ur Flexed-Arm Hang. This is when u stand on a chair that is tall enough to get ur chin above the bar, & then just hang there with ur chin still above the bar for as long as u can (nudge the chair out of ur way with ur feet when you're ready to start). Do this 2 times a day, 3 times a week.
Remember, these r the minimum amounts per day & week. You can always do more as long as u r not hurting yourself! And one last tip, always stretch for at least 5 minutes, before & after ur work-out.

Good luck!