There’s always the possibility that you’re misinterpreting things. I’m only getting one side of the story. But let’s assume that you are absolutely accurate in your letter.
In that case, there are a number of red flags that this relationship has moved from being therapeutic to exploitive. My first concern is that you’ve been seeing a therapist for 10 years, since you were only 14. At the very least, it suggests that your therapy isn’t working. Therapy is supposed to be, as you said, a temporary support and learning process. Of even more concern is that you seem to be feeling worse, not better, as a result of your interactions with your therapist.
Then there are the issues around sex: I can’t imagine a therapist suggesting that someone cheat. Reconsider a relationship? Yes. Cheat? No. The term says it all. Cheating is dishonest and usually only leads to feelings of shame, guilt, and regret. Most worrisome of all is that your therapist has told you many times that he finds you attractive and has said that he “likes” to talk about sex with you. You are right that it’s not at all unusual for a patient to have a crush on her therapist but that should become a topic to work through with the therapist maintaining clear and consistent boundaries. And counter-transference is what therapists deal with in their own supervision, not with the patient. Your therapist should have immediately understood he needs supervision when he found himself saying that he wanted you to continue as his patient for his own selfish reasons.
In an ideal situation, you would be able to talk with your therapist about your feelings as a way to figure out your part in relationships and tp practice handling conflict. But that assumes that the therapist is trustworthy and able to do only what is in your best interests. It’s not about what does or doesn’t “sit well.” It’s a matter of professional ethics.
In a situation like you describe, I worry that to share your dreams and feelings with your therapist would lead to more confusing conversations that make you feel guilty for wanting to leave. If that is the case, it may be more reasonable for you to interview a few therapists and find someone new to talk to. The very first issue you will need to deal with is your experience with your former therapist and how it is likely to impact your trust in your new one. Your new therapist may also be able to help you decide whether your longtime therapist’s behavior should be reported to the licensing board.
I’m truly sorry that you are coming away from a decade of treatment feeling depressed and confused. As with physicians, our job as therapists is to first do no harm and then to do our very best to do good. It grieves me to hear of situations where a therapist loses his or her own bearings in such a way that the patient gets hurt. I encourage you to take charge of your life and to find the supports you need to get comfort and to heal.
I wish you well.