Where you would want to go from here in the relationship will also depend on her. It seems that you believe that she is not committed in the way you would like her to be. If you do not believe that due to the age difference, her ex boyfriend and the fact that her friends do not know about the two of you (for the last 2 years), all of these are red flags to an objective observer.
It is not unusual to feel jealous even if she is keeping a long distance amorous connection with someone if that bothers you, she ought to respect you.
The two of you will need to sit down and figure out what each of you want out of this relationship. Couple's therapy also helps if that is something you want to look into it with her.
The two of you will have to talk about what kind of a relationship you may want to keep if you are not together as a couple. That would have to be a mutual understanding.
It is possible that you have become used to and attached to her. It is possible to be with someone else since nothing in life is a definite and things and people change.
As far as her being a therapist, if you were of legal age at the time of the start of the relationship it is still odd to not tell others about the two of you.