Please don't take this the wrong way but I'm pretty sure ECT is an absolute last resort. Have you tried all variaties of meds? Stuff like lithium, MAOIs, TCAs, or combos like Venlafaxine/Mirtazapine. Have you been hospitalised in the past for depression? I was in a bad way yesterday when I saw my pdoc and was cutting my arms over the last couple of days, I told him I was worried about my safety, self harm etc...he didn't even consider hospital and just got me some talking therapy and an increase in meds.
I'm not saying your doctor won't consider it, but there are many avenues to explore before that. Saying that because you are in such a bad place right now could you not consider going to A and E? Or do you have a Crisis team number you could call? If you are thinking about ECT I don't think you should hang around till Monday.
I know how bad things can get as years ago I begged my GP for a mood stabliser, even got to the point I ordered some lithium online from India.