So, you dated for 7 years but didn't get married or move in together, then moved back out after only a year?  She didn't want to get a job near the location of your residency?

This is already sounding unhealthy.

&gt;she was in a dying long distance rellationship and was really struggling to fit in 

Lather, rinse, repeat. 

Seems like the same pattern repeated itself in your relationship. The common denominator here being her. 

&gt;despite having a troubled rellationship with her parents

This is a pretty common red flag. Can result in attachment issues.

&gt;I've(sic) fallen deeply in love for her and supported her rellantionship,

This rarely ends well. This is you trying to "Friend your way into someone's pants." This is a somewhat crass way of putting it, but the reality remains that you're not being upfront about what you really want, and not prioritizing your own needs. 

As a physician hopefully you've run into cases of patients prioritizing the needs of their family members to the detriment of their own health.

 &gt;though as soon as it endend we started dating. 

She immediately jumped from one needy dysfunctional relationship to the next one, without taking time to grieve and get her own situation in order. This is not a good precident.

This suggests her reasons for being in the relationship are strongly driven by fears of abandonment and fears of being alone, and less to do with admiration, respect, attraction, love and trust.

&gt;During the next 6 years we've been in an amazing rellationship, though I've felt that she put a lot of pressure in the rellationship to compensate for the unhapiness in her academic/professional, familiar and social life. I was her main support here and she never managed to develop strong friendships in this town,

I'm sensing a [Pursuer-Distancer Dynamic](https://www.gottman.com/blog/how-to-avoid-the-pursuer-distancer-pattern-in-your-relationship/) in your relationship. 

This is often seen on people who have [attachment dysfunction. ](https://www.psychalive.org/anxious-avoidant-attachment/)

&gt;I had the best 9 years of my life. She just changed. 

Well, in hindsight it was far from the best 9 years of hers, but would you have really known at that time?

1) she wasn't truly communicating her true feelings. Seems there's a huge disconnect in emotional intimacy here. It's unfortunate that many people assume that if the physical intimacy is good, then the vital emotional intimacy is all taken care of. People often confuse physical closeness with genuine mental closeness on a relationship.

2)the distance in your relationship made you almost completely oblivious to the issues and distress she was having. 

This may have been semi-intentional on her part. [She clearly didn't wish to be vulnerable](https://www.ted.com/talks/brene_brown_on_vulnerability/transcript?language=en) that way, by  communicating what she was really feeling. Again, this kind of thing is common in people who fear abandonment, which relates directly to attachment. 

&gt;I wonder is there's any secret motive. I don't think she had an affair.

Going out "Clubbing" often with "friends", not answering her phone for days, not wanting to spend time together.....

I'm not saying she did cheat or didn't. Wouldn't surprise me if she did though.