So I met a client earlier on this week, and just can't get him out of my head..I think this was mainly to do with the activities of the session (included BDSM my being sub)  as its something I often fantasised about in my private and always was quite embarrassed about it. Everything was just brilliant, such a surreal experience- can't forget the whole thing, and the thought that I'm not gonna meet him again makes me sad.
Something which has never happened to me before in personal let alone professional life.
I know it will sound way out of order, but shall I email him and tell him that I would do it again free of charge (I would) or that would be just too wrong and I would sound ''stalkerish'' ?

Anyway, I doubt that he would like a relationship with an escort, which upsets me, but maybe is for the better.

Agree. Keep him paying as long as he comes. Even if you are tempted baaadly. Some of them just waiting for freebie. I had one like that just recently. He believed, that because the sex was awesome (and was), I shouldn't be charging him, because 'I wanted it too'. No comments.

As per sub experience - I know your pain. I am sub myself, and I know how difficult is to find a suitable lover. I do not offer BDSM in my menu though, only if I see that somebody could be into it, and I know him well. However submissive nature helps in this job, at least this is my case.
Ping me on priv, I might be maybe able to help:)

One of the reasons clients book us is not just for the great sex but also so they an be left alone afterwards. You've had some great sec but really you got to look at this as a professional. Perhaps now you know you love this side of things you can look at ways of incorprating it with your work and researching becoming a professional sub?  You can have fun like this with other paying clients.