Here are some questions for you to think about:
Are you eating a healthy, varied diet every day, on a schedule of some sort, with limited junk food, caffeine and sodas (sugar or diet)?
How much plain water do you drink every day?
Do you smoke or vape any substance, or are you exposed second-hand smoke?
Do you work or go to school? Or did you recently graduate high school and are in transition?
How much screen time - phone, TV, computer, gaming do you do each day?
How much physical activity do you do each day - house & yard work, work, exercise, walking, biking, etc?
Do you keep regular hours - getting up and going to sleep at similar times, or do you nap, binge watch shows into the wee hours, work rotating shifts?
Do you have your own place, or live with family?
Are you financially and physically secure or do you worry about food, money, housing, future?
Do you have regular social interaction, in person or distanced, with people your own age who you actually know personally?
Are you in a relationship, and is it stable or shaky?

Now, think about when those bad days happen - are they related to any of the above? Maybe you could keep a journal for a month - what you do, eat, drink, feel - and see if it reveals anything about when you feel bad. Then you have something to evaluate to try to find a root cause or to take back to your doctor.

Absent any real findings by the doctors, and their concern about anxiety, I would guess that at your age, you are needing to make a lot of decisions, that may be true even if you don't recognize it. And people who "hang out" a lot sometimes don't maintain good and regular eating, sleeping and exercise habits, that can contribute to feeling bad.

I hope you can do some detective work and figure this out - it's no fun to feel lousy. Stop by any time if you have more concerns, and we can chat.
Sue