If you have not yet got the hang of swimming with a central snorkel yet then please give it a go. It is one of the most effective swim aids you can invest in <Available here>. Unless very confident in the water or a former scuba diver these seem to work best with a nose clip. Inhaling with the face in the water can really confuse the brain and water can be inhaled through the nose which is horrible!
Before launching into a length of full stroke just get aquainted with the snorkel by putting your face in the water in the shallows and work on easy breathing in and out while static. Then perhaps some legs only with your face immersed. Then work up towards some full stroke. Drills will become more accurate as you focus on your body position and not on when to time the head movement for the breath.Keeping the head still is a great way to watch what your arms are doing under the body as they pull you forwards. You will spot wide sweeping hand pathways that will drive you from side to side. You will see the palm face down driving you up rather than the palm pushing water backwards to send you forwards. Not turning the head to breathe will also give you a chance to break the dreaded straight arm pushdown issue affecting many.
Have a great week of swimming