I have 2 swollen lymph nodes left posterior neck, 1 groin, fevers, night sweats, weight loss, itchiness, and I'm utterly tired. What's wrong?

See your doctor. Fever, weight loss, night sweats, fatigue, itcheness and enlarged lymph nodes warrant further investigation in any age group and shouldn't be ignored. The constellation of symptoms you are giving can be seen in lymphomas, infections or other systemic illness like sarcoidosis among others. Only a physician can guide you to the next step to find the cause. Please don't wait and see your doc.
Need a work up. . This requires a work up. With your combination of symptoms it could be something as dangerous as cancer or something relatively benign like a viral infection.. See your doctor asap.