He is misusing his professional knowledge. Yes, he is not being nice - he is falsely analyzing you. Which is not nice. And, it is wrong. When you email over and over again despite knowing that you should not be emailing, you are being anxious and neurotic, but not manipulative. He should know better.

On your end, you are not getting it. He does not want you to email - you should get it. You are in touch with your feelings - you explained what exactly made you feel jealous when he was a Fb friend with another woman but not you. So it was not sex that made you jealous, but the lack of social connectivity between you and him - you envied the other woman with whom he has social connectivity.

So, you need to re-rank the priorities in your mind. It is an exercise for your mind, done internally in your mind - you do not have to interact with him in order to got through this exercise.

In your mind, there is some kind of a ranking that places sexuality under social connectivity. Due to having this ranking in your mind, you feel slighted by only being his sexual partner, without being his FB friend. You further feel slighted by not having enough email interactions with him.

If you work with this ranking and place sexuality on the same level as social connectivity, you will stop feeling slighted, and might stop emailing him as much. Just accept that you have amazing sexual chemistry (you wrote that you do) and that sex once a month is all you need from him. And settle for that. There is nothing wrong with having a partner just for sex; the ranking in your mind makes it wrong/bad/insufficient/incomplete for you. Work with your mind. Analyze the assumptions and stereotypes that were implanted in your mind by your family, school, and society at large - they are probably responsible for the ranking in your mind.

I caution you, though - mental health professionals who abuse professional knowledge and professional terminology in their romantic relationships are dangerous people (I was married to such a man). If he keeps doing that (which undermines you), at some point you might feel that nothing is worth even the great sexual chemistry you two have. However, if you - in your mind! again, it is purely working with your mind! - accept him as just a sex partner, you will instantly become less vulnerable to his techniques and attempts to undermine you, and that might enable you to prolong the relationship with this guy.