From one who's "been there, done that," I really doubt that those supplements and fish oil had any real impact on your anxiety. If they did, it was because of the placebo effect. You expected them to help you, and so they did. When you stopped taking them, you expected anxiety to come back -- so it did. The good news is you've proved to yourself that your anxiety is self-inflicted, meaning it is caused by "stinking thinking" -- and that you have within you the ability to manage it. I highly recommend seeing a counselor for some cognitive behavioral therapy (CBT) who can help you overcome your distorted thought patterns and conquer your anxiety -- or at least help you manage it. Best wishes!
I remember the supplements you were taking -- I don't think the particular combination you were using would do anything about anxiety. Fish oil has been connected to reduced depression, but not anxiety, and it depends on how much of it you take, but it's a good supplement for overall health. One thing it does is reduce inflammation, and many believe that's a cause of mental illness as well as a host of other problems. But to really use natural medicine to treat mental problems, you have to go at it in a disciplined way and you have to go after different organs. A book called Natural Highs by Hyla Cass, a psychiatrist at UCLA, provides an overview of how supplements are used in combination. But natural medicine would also include lifestyle changes, dietary changes, and therapy. The above suggestion to try CBT is a good choice. As far as supplements "covering up" anxiety, no, it doesn't do that, and a placebo effect would e very short-lived. Getting the body into balance is helpful, but again, the supplements you were taking were not targeted for what ails you. Good luck.
Fish oil. An cause anxiety in some people.
Vitamin D3 supplements need to be taken for life and magnesium is necessary to go with it.
Get your Vitamin D and magnesium checked. Maybe B12 too.
Deficiencies cause anxiety, depression and more.
25 OH Vitamin D