Does being diagnosed with hyperprolactinemia mean that you do have a tumor in the pituitary?

High prolactin. Not necessarily -- high prolactin can be caused by other things ie medications, pregnancy, stress, thyroid dysfunction , nipple stimulation, lab error.
No. There are other causes of high prolactin beside a tumor in the pituitary such as pregnancy, breastfeeding, breast stimulation, mental stress, chronic kidney disease, hypothyroidism, polycystic ovarian syndrome...Depending on how high the level is, you might need a MRI of the pituitary as part of the workup.
MAYBE. Prolactinomas can be treated with oral medications. If visual complaints, then there is a surgical option - transphenoidal removal, basically through the nose. Talk to your doctor to decide what is the best option for you. Remember, this is a begin tumor. In pregnancy prolactin levels rise and with breast feeding even more, this hormone is the stimulus for milk production. There are other causes.
Hyperprolactinemia. Could possibly be from a microadenoma of the pituatary. Other causes are hypothyroidism. Need MRI of the pituatary to rule out tumor.