how to break it off with sb?

Dear fellow fapstronauts,

I am posting because I feel I should end meeting some girl and for some reason I was postponing it for long just trying to avoid it.

The circumstances:
I asked her out on a date a couple of months ago, which she gladly accepted, and when we've met the second time we became already intimate. After that day, I started to feel bad, as if I just exploited her without even knowing her properly.
I told her so, and subsequently we did not meet for about two months because I had a clinical stay. We stayed in contact through letters, though.
As soon as I returned back home we started to meet up again occasionally but agreed on to do that without any sexual contact (even no kissing) just to get to know each other.

Every meeting we've had since then left me with mixed feelings: she seems to be very interested in me, but I kind of feel alienated by her. Also I felt regrets to being so close with her in the very beginning. I find her interesting, but to me this is not enough. During my reboot I had so strong feelings for other women (strangers) that it feels like playing with her feelings to continue dating.
So I decided to tell her I don't want to meet her any more.

I want to write her an EMail NOW but I am somewhat blocked and thinking like crazy what to write. Don't want to hurt her although it's a stupid goal. Moreover, don't want to let it slip into a discussion about some whys and ifs.

Any moral support is welcomed
lionace

Update: I already sent the EMail insofar this post already served its purpose...