My son was much the same around that age, but it definitely got better! I remember calling my husband frantically for an hour because I thought he was going to be home at 5:30 - he didn't end up getting home til 10; he was asked to stay back at work. He never did it without checking with me again. I must have sounded hysterical when he finally called me back.
We used the bouncer a lot too, and while we tried out a couple of swings, it wasn't for him. He liked me to sing to him while he was in the bouncer if he was really upset. Before we got the bouncer, I used to sit on the exercise ball and bounce or rock. He seemed much more content if I did that.
A chiro or osteo could definitely help, just make sure you get some recommendations for someone from your local area.
If you need a break, put her down and walk away for 5 minutes. Easier said than done (I know!), but you won't be any good to your DD if you can't function any more.
It should improve soon. I hope you find something that works for you.