Well, fuck. So many thoughts and feelings crowded into David's head and body all at once that he found it difficult to process it all. He pulled his hand away from Bill's and ran it through his hair, tucking the golden curls behind his ears compulsively as he looked down at the ground between his feet in an attempt to steady himself and work out what to say. His other hand emerged from his jacket pocket at about the same time and scratched reflexively at his chin, his tongue wetting his lips yet again as he shifted in his seat, sitting forward yet turning to face Bill a little more.
As far as confessions went, this was hardly the heartfelt declaration he'd envisioned on their date a few nights ago. He'd believed Bill would be enthusiastic, excited, trepidatious but abuzz, possibly even a little more loving... but it hadn't worked out that way at all. Four nights ago, there'd just been surprise and awkward avoidance and a crushing realisation that they weren't wanting the same things at all. Now there was this and... truly, it felt hollow. Certainly, Bill had confessed that he liked him but telling him that he would date him simply because he didn't want to regret it later in life was hardly positive. It was like a concession - to his libido when his head said it was stupid. There was no hint of what the mortal's heart had to say, which was what hurt the vampire most, really. Bill's words alluded to the fact that he believed he was a vulnerable mortal - despite the fact that David had assured him otherwise - and that he believed his days on the Earth were numbered, therefore he might as well try to enjoy it while it lasted.
And suddenly, it was all very clear to him, the choice between Bill and Cain. Bill... his heart had wanted it to be Bill from the beginning, because he was so quirky and intelligent and sexy, but it hadn't worked out that way and now David knew why. Bill would take a chance on him, because he liked him but, since he was likely to die soon anyway (in his head) there was no point throwing himself into anything scary. Especially not anything where he might contemplate becoming a vampire - even if nobody was actively trying to sire him at this stage. Everything with Bill was a trade off, a maybe, a logical rationalisation of feelings that David didn't share. David really liked him and he just wanted to spend time with him, it was all very simple to him, but Bill didn't see it that way.
This mortal was too aware of the imbalance in their relationship for it to ever work properly, and though he couldn't say Cain was any different, he approached it in different ways. Cain was grateful and appreciative of their differences, he didn't spend his time worrying about what sort of dangerous lifestyle he was leading, he was excited and passionate about spending his time with David. Yes, he was too worshipful but David was confident that that would fade over time and they'd reach an equal regard for one another, despite species. He couldn't see that happening with Bill... well, ever, at this stage and even though he wanted to work through that with him, his logical side told him it wasn't worth it. It would just mean more hurt for him in the long run, because already Bill wasn't going into this with his heart on his sleeve and his head thinking about fun; he was slinking in, tip-toeing through the quandry of their differences and focussing on the parts that he did like, while trying to ignore all the rest of it that he couldn't cope with. It wouldn't work between them, David saw it clearly.... but, unfortunately, that didn't make it hurt any less.
"I do want to date you," he said cautiously, lifting his troubled gaze slowly from where he'd placed his hand on Bill's thigh and up to regard the mortal's beautiful brown eyes. "But... I'm seeing someone else as well, so... it wouldn't be exclusive," he admitted apologetically, watching Bill's reaction carefully. He expected that the mortal wouldn't take this news well, but he doubted it would hit him too hard, considering he didn't seem to be too caught up in the idea of them dating - not for any particularly romantic reasons, anyway - so it was the best way to go about it. Giving him this information was his way of giving Bill the power to break off the relationship on his own terms, perhaps to feel like he'd been cheated on, wronged and thereby that he was gaining vindication by being the one to back out of it. He was handing Bill the power, because the mortal didn't ever seem to feel he was in control. It was the least David could do for him, considering how much he cared.