I suspect that all the stress of getting your dad moved has caught up with you and now that he's actually settling in, you have time to think, which you probably didn't have before. Your dad is very lucky that you are caring for him so lovingly but perhaps there has been nobody there to care for you which has added to your sense of anxiety? . And possibily you never really had time to grieve properly for your mother because you were primarily worrying about how your dad would cope on his own?
My suggestion is that you both try and spend some time together doing a few pleasant things, and perhaps try to find some activities or social groups which your dad could join, to help him make a few new friends and contacts. Also, now is the time to take a little time out for yourself. You have done all the stressful things and got the house move behind you. Those of us who have cared for elderly parents will recognise your plight. We take on their anxieties as well as their own and sometimes it can seem a heavy burden if there's nobody to share it with. Try and set aside a quiet time for yourself every day. Take a short walk. Go and listen to the birds and watch the seasons unfold. Practice deep breathing to help yourself relax. You deserve a few pats on the back for looking after your dad so well. So give them to yourself.