At 18 years of age there are a number of possible causes for your symptoms.
is quite common at your age and would account for some of your symptoms. I guess your diet is healthy but you need to ensure you eat enough to sustain you through your rigorous training regimen.
should be consiered. Are you getting enough rest? Do you have any niggling injuries that are preventing you from achieving your goals. Stress
can cause these sorts of symptoms.
I would be difficult to be more specific than this but I hope these suggestions may be of help.
Dr K A Pottinger