Hi Luis, a dilated heart is almost always due to being overworked or under stress unless there is heart muscle disease caused by excessive alcohol, drugs, congenital defect, etc. Treat the underlying cause such as stress and/or high blood pressure (the usual cause) can/will reduce the heart's workload and reverse the enlargement and increase the EF.
The enlargement causes the heart to not effectively pump and that is evidenced by your 38%...The ejection fraction (EF) is the amount of blood the heart pumps with each heartbeat. Normal EF is 50 to 75%. A 38% EF is usually not low enough to cause the symptoms you have, but it is possible. However, there are individuals with an EF in the 20's that function very well as their system compensates for the deficiency.. You are young, history of exercise, etc. and should have compensatory factors that would help you. Has any other health issues been diagnosed? What tests have you had? What medication do you take?