Kitten - sounds like your week has hit rock bottom and my sympathies to you in trying to cope with a distinct lack of support.
No point in starting an argument with your husband while you are feeling so fragile. Might I suggest (its only a suggestion, please don't shout at me), trying to explain to him how you feel and how hard you are finding things at the moment. Say that you are trying so hard to keep it together and you would find it so much easier to do if you had his support (and explain to him that actions speak louder than words). Don't have a row with him at this stage since you main priority is firstly you (since how can you look after your dad and your son if you are in bits). Take only little steps but more importantly, don't feel bad about crying. It's part of the coping mechanism.
Caj is right, your period is probably only late because of the stress you are under. But if you are concerned, why not see a doctor. He will perform a test and may even suggest some mild sleeping tablets just to help you get a good night's rest. With all you have going on right now you do need your rest.
Sorry, I don't know what else to say. I have never been in such a sh!tty situation so these are only suggestions without any real knowledge of what you really should do. But all the best.