I need to start doing pull ups but they're so hard
Can you do Chin-ups? Chin-ups will lead to pullups.
If you can't do chinups either, there are many ways to build chinup strength. The assisted machine is one of them (I used it for a couple of months before I could do a single "real chinup"; basically did a linear progression on the assisted machine where I would decrease the assisted weight by 5kg every week) but negatives, lat-pull-downs and band-assisted chinups all work as well.
Bands / negatives are probably best because they are the closest to a "real" chinup. When I transitioned from the machine to the real thing, my biggest issue was lack of stability: I was swinging like a pendulum, because the machine is holding you from underneath and doesn't really train that part of the movement.
I've posted this before but it's a great guide, so it's worth reposting:
Developing a Pull-up
As far as chin ups/pull ups go, I have a serious "swinging" problem when I do them. I usually have to stop at the bottom so I can stop my body from swinging a bit, and then continue.
That said, I can only bust out sets of 5-8. I think I seriously need to drop my body weight to be able to do them decently.
I had the same problem and the way I fixed it was by doing very strick chinups from a deadhang. If you are swinging it's also because maybe you lack abdominal / oblique strength (fixed by deadlifting / squatting / hanging leg raises).
I don't think it's a body weight issue. I weigh 225lb and can do sets of 12.