As a right arm swing and seam bowler, I'd agree with Nick. Concentrate on simplicity and consistency. While you worry about everything you will find it hard to control the ball.
Put the hours (and it is hours!) in to determine your run up. Spend 6 hours a week running in and bowling - you will find a length of run up that you are comfortable with. Losing rhythm prior to the delivery strides suggests that your run up is not the correct length. Do as someone mentioned and reduce it, almost coming in off a walk in. When you find a length that is comfortable, keep using it.
In addition, as you run in, look at where you want the ball to bounce. Even as a swing bowler, this will aid you in your delivery. You'll be surprised at how effective this is even with the ball swinging.
Don't try and jump. it puts you off balance and all over the place. Just run through the crease.
Finally, practice. 10,000 hours is the number quoted, and unfortunately for anyone bowling with any kind of pace, it is necessary. You have a lot of levers to co-ordinate and the more you do it and it feels right, the better it will become...