Hi OP,
It does sound as you are quite unhappy and it goes beyond just being overweight. It sounds like you have given up. And that i think is what would make people not interested.
Rather than looking for clothes to disguise your size, you should look for well fitting clothes in colours which suit you. That will automatically make you look smaller, as will walking tall and straight.
What styles do you like on other people?
There are lots of shops now doing lovely plus size stuff. A few have been mentioned above but i really like very, asos and new looks plus size ranges.
I also go to bloggers for inspiration, here is one i really like
fullerfigurefullerbust.com/
i agree that making an effort with your hair and make up helps as it shows that you value yourself. that doesn't mean using a lot of product.
your evenings will seem endless so why not get out and do stuff without the goal of meeting a bloke? a hobby doesn't have to be weight loss related and increasing your social circle will do a lot for your happiness, which in turn might make it easier to eventually meet a bloke.
what things do you have interest in? do you enjoy cooking, reading, crafts, sports (watching if not playing)?
are there any community endeavours in your town? we have litter picking which is a great laugh and always end up at the pub afterwards. there is so much if you are open to it, and sometimes it only takes one small thing to start the ball rolling for massive change.
i wouldn't even think about dating sites at this stage. id think about looking at yourself and going - fuck yeah my hair looks fab. or i really love these shoes.
and then going out and letting the world see - not just men.