How can I get flying again after FAA medical rejection for anxiety two years ago?
In general, as I do not have the guidance in front of me presently, if you have been diagnosed with an anxiety disorder, and later taken off the medication with no adverse effect, and the symptoms are absent, you have a high probability of obtaining a medical.

First, your primary care physician should document that you have been off the medication for x months.  Usually two years is good enough.

Then you should shop for an AME.  You want someone who is willing to work with you to get the documentation needed and submitted. Your initial application may be initially deferred, and forwarded to FAA Medical Headquarters in OKC for review. OKC has in the past taken calls on medical certification inquiries, but has also not taken them.  I would call them and ask for their guidance documentation. 

If you are an AOPA member, their medical support people are excellent, and will give you specific guidance, as to what reports and findings will be most helpful.

It is possible that you might need an evaluation by a specialist, a psychiatrist, to assure that you are not walking around untreated, and do not show any signs of GAD.  GAD is often considered a long term chronic disorder, and it is not uncommon for people with GAD to have the condition for their lifetime.  In your case, you will want it to be that the diagnosis surfaced with situational circumstances, and the condition is no longer an issue, and the medication is not indicated at this time.

As a CFI, I have had quite a few primary students, and one CFI student who had similar or even more significant psychiatric disorders, and as those were addressed and they were able to drop the medications, they were again qualified for a medical.  Also keep in mind that your road to Basic Med will initially require a 3rd class or higher medical.  So it would be nice to get this administrative matter resolved.

In addition to AOPA, there are places which primarily help pro pilots, but will provide excellent services to help guide you through the process and if you are qualifying, will help you get a medical.  They can be several thousand dollars, and in your case a year of AOPA membership would be very cost effective.

As an example, I had a primary student who had a history of suicide attempts.  It turns out that she felt she was trapped in an abusive relationship.  A couple of years later the situation was different, and her PCP and therapist records were all that was needed to have the FAA issue an unrestricted medical.

For air ambulance, if you are not playing a role which requires a FAA medical, then you will not need one.  In air ambulance, the typical roles requiring a medical are pilots.  I don't know of any air ambulance outfit which requires a FAA medical for their EMTs.  You could always ask at a place that you might be interested in employment.

The FAA medical practices are in place to mitigate perceived risk.  People have situational circumstances in their life which may be outside medical issuance, but their situations also change.  To a degree, the FAA generally recognizes that.

Good luck pursuing your interests.