Longer boats go faster than shorter boats. The same goes for your body. The longer your body during all phases of all strokes, the better it will hold its speed during the slight pauses between strokes. That keeps your body longer while your other hand completes its stroke and takes over the front position. In breaststroke, after pulling, stretch and streamline both arms forward and keep them there until after you complete your kick.
Longer body equals faster body.
Improve your hull design. Though you didn't get to choose the body you were born with, to a certain extent you can design the hull or vessel in which you ride the water. Imagine yourself swimming down a very narrow tube, as opposed to, say, a large sewer pipe. When you get into the more fishlike side-lying position in freestyle and backstroke, the water passes across two surfaces of the body, chest, and back, and has to travel only half as far to get out of your way as when you're chest down with almost all the water flowing under you. That reduces drag by as much as half.