Hey Butterfly,
I'm not sure how you made him feel insecure, but that's a turn-off. At least for us scorpios 
Sounds pretty turbulent, and if I were you I'd probably forget about him unless you're willing to live by his rules and not get hurt or paranoid (which may very well be well-founded). But yeah, that's not an easy thing to do. So there...
Good luck
No worries THW, always forget to address my post anyway.
So what is exactly this sexual touching cuspglyph?
...the smiley was a response to thehangedwoman
Can you define sexual touching pls? Am not really getting that...
What the what are hiding? 
Quite odd comments I have to say Hangwoman....
Nonetheless, thehangedwoman is on to something in her first line. I.e.The best "revenge" is living well...
I say dont write the letter, and if he contacts you again, give the impression that you have moved on and is happy and dont need him. Be nice to him though as you were when you first starting dating. I`m talking the way you were in the very beginning.
Let him pursue if he is interested (read: a good match for you), which he will surely do if "the feeling" is there. Us scorpios are determined and will do what we can to acquire our target. So don`t worry that you would "ruin your chances with him" by not writing the letter.
PS sorry about the weird and changing fonts, my keyboard is Canadian and it sometimes switches between English and French.
It`s not that hard...
To me it sounds a little bit like you don`t know what you want yourself.
He obviously like you, since he calls you for several hours. I think you are the problem here...
Youve pulled away too much and not engaged in intercourse, leaving him an impression of being uninterested in one way or the other. He seems to respond positively whenever you say something nice to him, like: "Ive been thinking of you", so keep that up. Dont do it too much tho, you dont wanna give everything away. But yeah, next time you see him def have intercourse, and show him that you are into him. He`ll def respond positively. You have to submit...
Being a scorpio myself in mid-twenties, I would probably also pull the plug on a girl who doesn`t show enough interest and doesnt know what she wants (and doesn't put out). Cus that's weakness is in our book and it's a turn-off. Deal with your insecurities and either go for it or don't and let it go.
Oh yeah, I also second what wubbledoo said regarding whether he`s into to you or not (at least at the moment).
Ive been in a similar depressive situation, and although in that time I craved more solitude than usual, I would readily call anyone up whenever I felt like being social. So if he felt like seeing you, hed do it in an instant, and would even use you to get back on top and "heal" or whatever. But youre draining energy from him instead, when youre that clingy... Thus he cuts you off.
Wubbledoo is correct... Sorry to say it, but you are giving way too much away to the guy emotionally.
Being a scorpio male myself (mid twenties), and sexually active with different (however consistent) women, while being involved in a long-term relationship with a pisces, (none of whom have any idea that there are other women in the picture), I don't think this guy is very interested in you. At least not at the moment. You've given away your "mystery" and he sees through you now and probably knows you wanna marry him etc etc.
I've broken up with one of my gfs cus she became really "sticky" and corny and pretty much gave away "everything". I knew I could have had her for life and she would have done anything for me to make that happen, but by that time I'd lost all interest, including sexual.
Thing is, and this is what you have to remember if you really want this guy, after I broke up with her, she got upset and never contacted me again... About a month later I sms'ed her cus I didn't want her to feel like I had just used her, but that I actually cared (which is true), but she didn't answer. I tried again a couple of days later, and she replied with a very happy message where she wrote that she was doing well and was feeling great. I smsed back but got no reply. When I smsed her again, a couple of days later I started inquiring into what she had been doing in the past month and a half. She wouldnt tell me, and still I have very little idea, Im still trying to probe for info. She did sort of imply shes seeing someone else, and I also saw her in the passenger seat once in her car, speeding away, with a male driver behind the wheel. Ive additionally asked her several times if she wants to meet up, but she says she doesnt want to. Thing is, I know she would take me back if I really tried, but still she has managed to intrigue the hell out of me, and I really want to see her again and have sex with her again. Shes gotten her mystery back by acting slightly aloof and very distanced. And even though I think this may be a game on her part, I really want to see her again. Had I not been in other relationships with other girls, which keeps me sexually saturated, I would immediately do whatever I can to get her back... So, try that. But it has to be convincing and consistent, otherwise he may take you back, only for you to make the same mistake again and give him too much, which would result in him dumping you again.
So yes, give him space, do not contact him, and if he does, act distanced and uninterested (like youve lost interest). I really wouldnt pursue...
Hope that helps...
PS - Lots of scorpio men dont cheat Im sure, I think I just have a very heavy sexual lust, and was betrayed once, so there...