So very sorry about the death of your dad madmomma and coming at such a time when your hormones are all over the place anyway with a very young baby. Do you feel depressed at all - I ask because most depression is about loss, and you have suffered the loss of someone who was as you say "your world"
Your DH is obviously working hard, but not enough to keep things going by the sound of it. You are one of thousands of people who are struggling in this country at the moment, but that doesn't make it any easier to bear I know.
Could you try CAB as about 80% of their work is now debt related.
You have so many things to cope with all at the same time, so you do need to monitor how you are feeling, and maybe talk to the GP - you may need meds but then again it may just be the situation you are in that is causing you problems. Nice to hear you have a sensible 14 year old to help (good job she's a girl!) but she must be worried about you.
Is your mother alive, or do you have any other relatives who could help. You say you have no friends at home - have you moved house or have you lost touch with friends. Sometimes HVs can put you in contact with another isolated mum. This was a life saver for my friend's daughter as she was on the brink of clinical depression, but having a friend with a baby of a similar age made a big difference.
Hope you get your toddler off to nursery for a few hours. He sounds like a fairly typical 18 month old, but wearing nontheless.