Hi mokey. I'm experiencing something very similar - I'm about 16 months in and I'm really struggling with the PhD (change of topic is making me feel miserable).

Have you tried speaking to an advisor (if you have that system), or have you got access to a confidential academic advisor in the uni - I found that speaking to someone not connected to department or PhD was quite helpful (Even just to get some reassurance that my problems were "real"). I think the question you need to ask yourself is whether you feel you can achieve the PhD (with whatever changes to your routine/supervision may be needed) - could you "put up" with the PhD/supervisor for whatever time you have left? Could you even change supervisor? Like yourself I have a keen interest in academia (particularly clinical psychology) but I'm not sure whether to start a new PhD elsewhere, or whether to just try and get this PhD back on track... Hope things get better!!