I have spots of my upper back and arms it's like acne and if i shower like once a week i get only abit but if i shower more often i get more spots why

Acne and similar: At your age it is very common to have acne, but certainly there are other skin conditions that may look like it. One consideration is atopic dermatitis which sometimes can present with lesions that worsen after showering more often. There are other possibilities as well but you need to be seen in order to definitely tell what it is. Consult your pcp or dermatologist.

Counterintuitive: As counterintuitive as it sounds, but plain water applied in excess (frequent showers) dries the skin out and can cause reactions like the one you are describing. If you can't reduce the number of showers you are taking, you may want to try a moisturizing lotion after every shower. See if that makes a difference.