Uhm, since you're on HRT, it's not exactly the same kind of arousal, and it probably doesn't feel nearly like a physical compulsion anymore. So I'm not sure if it'll work the same way, but for me, getting busy with something that makes me move physically mildly, and that occupies my mind as much as possible, used to take care of male-type arousal, sometimes. Like doing the dishes while listening to music.
My pseudo-scientific explanation is that the body only thinks it's appropriate to have sex when you're in a state of rest. If a prehistorical human is busy on a hunt or another task, it's detrimental to their survival to stop for reproductive acts, or to be distracted by the drive of them, as opposed to how reproducing is good for the transmission of DNA in a safe and calm environment. So if you're busy, the body switches from "it's safe, so let's reproduce" to "there's something more important, so let's bring back food and not die".
As for refraining from jumping on him, uhm... You could try to concentrate on "busy" dates, where you actually go and do something together, rather than just be together. Not as intimate, for sure, but the only way I can think of to keep yourself from wanting sex with a guy you like and are attracted to is to keep your mind off him.
If you want to masturbate, though, perhaps there is an alternate way that would satisfy you.
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Personally for me it doesn't work wonders, not to mention that my penis appears to be broken and unable to have an erection without hurting for days, but it did make me feel less awful to masturbate while keeping it immobile and stroking the tip as though it was female parts. Leaving everything inside my pants and doing it there had limited effectiveness too. My first girlfriend, trans, said she masturbated using mostly the rear end. The only time I tried it, very long ago, it felt like pooping and indeed caused me to poop, but well, people are all different.
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