Those kind of symptoms can be caused by a few things, so it's a process of elimination for you -- 1) yes, anxiety can cause all of them 2) so can low or high blood sugar 3) peri-menopause symptoms can do this 4) unbalanced hormones and/or electrolytes (vitamins & salts) can as well.
Now, you are only 21 y/y, so I doubt that it is peri-menopause but it could be hormone related. I have had both the anxiety and the blood sugar issues;so I am on Metformin for the blood sugar, and have meds for the anxiety which I ONLY take if really needed (which is rare now). I also am controlling my blood sugar with diet and exercise (esp walking).
Sometimes, I have even had a 1/2 cup of lite beer; and that helped for some reason, but I have read on the net somewhere that the hops in beer have a kind of natural estrogen in them (so there is the hormone thing again). One of my doctors suggested that the excess weight could be causing a kind of hormone imbalance in my body (which wouldn't surprise me), so we need to keep working on that as well; that may be why the beer works so well (but you only need a very small amount to remedy it). I think it helps with the hormones and helps calm me down too.
My TOM stopped for awhile and the doc gave me hormones for 6 months and it returned. When that happened again recently, I just added another Multiple Vitamin at night before bed and guess what came back -- my TOM. I am now taking 3 multi vitamin's each day: morning, dinner, and before bed as I have had a severe inherited Vitamin & Mineral deficiency since childhood). He had also suggested that I should take more meds and vitamins, etc to compensate for the extra weight I am carrying around.
Try to make sure that you are eating regularly over the day to keep your blood sugar levels balanced: have you had that tested? I have to take more vitamin supplements and eat a little more often (3 meals & 2-3 small snacks) each day.
You can get treatment for the Anxiety and could also add DE-STRESSING measures into your life -- start doing meditation and/or yoga breathing exercises to help calm yourself; and to increase your oxygen while resting, or before sleeping. Can you raise your upper body with some pillows as well -- that could help your breathing too. These are just a few ideas to consider while you are working on your weight issues.
I wish there were more doctors and/or health practitioners who would take a more wholistic approach (meaning whole body, mind, and spirit) to help us overcome these issues. It seems that all too often, we have to try and figure them out for ourselves. I hope something here helps you in some way ...