Hello from JustAnswer.
You have done the correct actions to prove that you are not having hypoglycemia, because checking a blood sugar during symptoms is the best correct step to exclude the diagnosis.
It is true that stress/anxiety can cause symptoms that mimic hypoglycemia. However, there is no test that can be done to prove that this is the cause. A definitive diagnosis is usually dependent upon excluding other possible causes of the symptoms. However, if the symptoms are worse on more stressful days, that is strongly suggestive. And if the stress/anxiety can be relieved and the symptoms resolve, that is also good evidence that the symptoms are due to stress/anxiety, although it is frequently not easy to relieve stressful life situations.
As for other possible causes of these symptoms, there are some people that can have profound symptoms due to hunger, even though the blood sugar is not how. Eating healthy snacks between meals can help prevent these symptoms. Some people try the snacks before checking their blood sugar and interpret an improvement in symptoms as a sign that they suffer from hypoglycemia, when in reality, they are merely managing symptoms that can occur from hunger.
Other medical conditions that can mimic hypoglycemia are much less common, but include reactions to certain foods, particularly caffeine or alcohol, and certain hormonal conditions, such as adrenal disease or pituitary diease.
So, it would be reasonable to try healthy snacks in the mid-afternoon to see if the symptoms can be prevented. If you can relieve some of the stress and the symptoms improve, then that would support that it is due to the stress, such as with self-relaxation exercises or yoga, but realistically, the stress may not be eased until graduation. If symptoms persist, then it would be appropriate to see your doctor for an evaluation for the less common medical conditions noted above.
If I can provide any additional information, please let me know.