Oh you have so much going on no wonder you are down. Don't think you can just pull yourself together, it isn't that simple and anyone who says that that's all you need to do doesn't understand what it's like to get as low as you are now. Doing things can help eventually , but like others I'd suggest that you went along to the docs and asked for help. Or your area might have a wellbeing service that you can self refer to. I put off and out off taking antidepressants when I was in a hole a few years ago in a difficult impossible situation. I thought I could pull myself out if it, but ended up hardly being able to get out of bed or do anything other than keep myself fed and in clean knickers. It takes time for the tablets to work and in the end I had them increased to a fairly high dose and they got me to the state where I could begin to work out how to deal with the situation I was in. I also was lucky enough to get counselling and benefitted greatly from a support group and a recovery course. I wish I'd not waited until I was so low, I'd be further along in my recovery but I guess I was afraid of getting hooked on tablets, in the end I started cutting them down myself, gradually, and had no bad side effects. It's hard to know what to do for the best when you are so down, if you did leave him now you'd be in the same situation but on your own and with all the trauma if divorce to deal with, and honestly it is not an easy thing to navigate. You may end up doing that, but you'd be in a better place to deal with it. Maybe now you just need to tell your husband that you are feeling down, and that you want to get help from the docs, what do you think he might say if you told him that
It is so sad to hear about your dd, obviously none of us here know what things were like before, but if the man she is with is encouraging her to cut off contact with family and friends it might be because he's abusing her, this is one if the things that abusers do, cut their victims off from those who could help, there may be lots of other things he's doing that she doesn't recognise as abusive, cutting her off is just one tactic abusers use. She may need you in the future
It's hard when you have no friends, and going and doing any of the worthy things people are suggesting won't get you friends that you can have heart to hearts with quickly. Your local vicar is there for everyone and asking if you can have a chat might be helpful, they can listen and sometimes just having someone who will listen is really good, he it she can't meet you every week, they have everyone in the parish to look after but there might be places they could suggest to find people to talk to.
You say you're off this week. Can you think if one thing a say that you could maybe do that you'd not normally do, that you could cope with. A health walk perhaps or maybe just buying a plant and potting it up when you get home, or just a coffee out, or just put some favourite music on or pick up the knitting needles and start something or just sit in the garden and listen to the birds. It won't make things better but for a few minutes it might make make things feel a bit better. If nothing 3lse get a docs appointment