I just got diagnosed with mono - my doctor said my spleen isnt enlarged & neither is my liver so can I drink alcohol? And when will I not be contagious

No. Alcohol is a poison that never did anybody any good, ever, so stay away from it.
Wish you 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.
Get HPV vaccine.