hello sending you hugs, hope you feel better soon.

I think I understand how you feel and it's horrid to feel your positivity draining away.

however please remember that things can get better. Also keep pushing your Dr for proper support, councelling, possible referal to mental health team etc
I've had bouts in past when I've been depressed, in lots of pain, or just finding it hard to motivate myself to even get up, and for me I find setting myself just one task for the day such as making a favourite meal or forcing myself out of bed and going for a short walk have helped me get the "spring back in my step".
It's at the times you least feel like doing anything that doing something has most benefit. I also think that following lupus diagnosis we all need to give ourselves time to grieve for the "old you" and adjust to the "new lupus you"
Personally the more "in control" I can make myself the better I feel. Actually just staying in bed too much does not help me so I try to force myself to be up before 11am every morning regardless of how bad I feel (believe me this can be really hard at times and I've even been known to go back to bed a few hours later but just the act of getting up, dressed and having breakfast often helps me)
I use a technique where I allow myself a whole "do nothing" day resting/ sleeping/just feeling sorry for myself with the promise that the next day regardless of how crap I feel I will do something - this something may be as simple as "I will phone a friend", "I'll read a chapter of that book", "I will have a pamper day where I have an aromatherapy bath, put on make up, try out clothes combinations to see if I can revamp my style with what is in my wardrobe" or it may be more ambitious eg "I will go swimming", "I'll tackle that job I've been putting off". Just doing something where I'm a bit more active or doing something other than thinking about how much pain I'm in does actually help me.
Friend can also be a great support so try re-establishing contacts with positive supportive people, or making new friends who accept you as you are "lupus and all"
Positive affirmations also work. (you say them or even better write them down -even if you don't believe it at the time they do work) here are a few:-
I love and approve of myself, I am safe
I trust the process of life, all I need is always taken care of, all is well
I now chose to create a life that is joyous and abundant, I am at ease
I allow my mind to relax and be a peace, all is well
I release the past, I live in the now in peace and joy
Divine wisdom guides and protects me at all times, I am safe
I freely and easily release the old and joyously welcome the new
I give myself permission to be all that I can be, and I deserve the very best in life, I love and appreciate myself and others
I am willing to change and to grow, I now create a safe new future
Hope this helps, best wishes for feeling "as well as you can be" soon
By the way your fathers comments are very likely to be due to the alzhiemers and not anything to do with you (my friends mother has this and often does not even know who her husband is) however try not to let his condition stress you out (stress makes lupus worse) and don't be affraid to ask for outside help for him, or to stop doing things that take your energy/ because people think you can cope - I think you need "me" time and there is nothing wrong with saying to others sorry I can't do that at the moment