try putting a broomstick across 2 chairs and then stretch *text deleted* body out straight with *text deleted* heels touching the ground. Then pull *text deleted* self up making sure your chest touches the broom. This could help.
press ups dont have anything to do with pull ups mate, completely different muscles, do negative pullups mate, (jump up to the bar chin over the top overhand etc etc, then lower yourself down slowly about 5-6 seconds, and do 3 sets of 6 of those twice a day, you will be able to do one in no time, then once you can do one, your away, just bang out one every time you go past the pull ups bar, and then once you get two start doing sets, and they will increase prob 1-2 every couple of weeks till then, i couldnt even do 1 about 2-3 months ago, but now i can do 8. it works bud.
Pull ups work different muscle groups so it is quite easy to be better at push ups than pull ups according to how strong different areas of your body are.
Also, although it may make little difference, when you are doing push ups, a little of your weight is supported by your legs. When you do a chin up all of your weight is on your arms.
Make sure you are doing your press ups in proper form as a lot of the other lads mentioned before me. If you are really struggling with pull ups place a chair underneath and use it to support a LITTLE of your weight. Slowly reduce the amount of weight on the chair and eventually remove the chair. I used to be exactly the same but now i can do 20 chin ups if i push myself.