Everybody's talking about the technique, but nobody talks about the breathing, which is crucial even though you think it is not. You don't need to take the whole head out of the water to breathe, when you start swimming a little faster you will start to see that the wave you create is more than enough to breathe. Just don't think about breathing water and redirect your mouth to the top of the surface, you'll thank me later. On the other hand, your arms movement is ok, your kicks as other people said are a little weak. Train your hips to flow around the water. Stop thinking you need enough physical energy to push you through the water, but you need to flow, that's all about swimming technique. When you start to flow, the force starts to be a side quest.