Sorry to hear you're feeling down Lisa, it's hardly surprising you'd feel like that now and again when you have a very difficult situation to cope with. You seem to be a remarkably positive person though, so I'm sure this is only a temporary low mood. We all get them from time to time, but we bounce back. Nowt else we can do, eh lass? 
Take some comfort and strength from the things you're doing to benefit yourself, for instance with your healthy eating and exercise regime. You're taking care of yourself, even if the person who should be isn't, right now. Keep your chin up. You're a strong woman who's doing very well to cope with a situation you didn't ask to be in. One day that situation will resolve itself, and I'm sure that better things await you.
Look after yourself, hope you feel better soon.
Take some comfort and strength from the things you're doing to benefit yourself, for instance with your healthy eating and exercise regime. You're taking care of yourself, even if the person who should be isn't, right now. Keep your chin up. You're a strong woman who's doing very well to cope with a situation you didn't ask to be in. One day that situation will resolve itself, and I'm sure that better things await you.
Look after yourself, hope you feel better soon.