My CPK was 254 U/L, should I be worried? Could it be ALS? 29/m, had it checked due to twitching of muscles, doctor advised no weakness on neuro exam

Listen to your doc. Your CPK is in the normal range for a young male. You may visit this site for info on this topic:
For good health - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Drink enough water daily, so that your urine is mostly colorless. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form.
Practice safe sex, if you have sex.