im a 17yr old male and im looking for a chest,upper arm and a lower ab(to get a 6 pack)wrkout?

im a crosscountry runner ,i practice everyday after school and mon. wed. fri sat and sun in the early mornings ,im also on the swim team so i swim tues. thurs. and fri. mornings.i average about 30-40 miles a week running and 15 miles swimming .im 5 ’9 and 120 pounds my BMI is 17.5 .its hard for me to bulk up soo im just looking to build enough muscle to look like i actually have muscle so i wont be as self conscious about having my shirt off -take into account that running will make the muscle smaller but more defined -i have scrawny arms but when i flex my biceps and triceps they are small but extremely defined but anyhow abs should be able to get pretty quick with a proper workout . so yea best answer gets the points ( i dont really have access to wieghts so if it can be done mostly at home it would be easier on me thanx