You may not have realised it but you have INDEED been using a nasty tone on me (or it's simply due to the fact that you're in a foul mood). Perhaps it's unconscious or what, but stop saying you haven't because it sounds exactly that way. Snappish, cutting, biting.

& I have been trying to play it down but when you use that tone on me for the smallest thing, of coz' I'll be upset.

& when I'm upset, you start saying things like I'm getting sick of you & all that, when I haven't (& I keep telling you that but you keep saying things like, 'I think it's just you!'). I have been telling people (yes, even as recent as yesterday) that we'll be getting engaged soon, & that we've settled on how many kids & so on.

Why can't you realise, that you may be the one who's getting sick of me instead?