I'm not a great one for giving advice on stuff like this but I'll just throw a few things in. You seem stuck in a rut and I think you probably know you've got to be the one you changes that and recognising that seems to me to be a good step forward already. So just some thoughts about things in the order they came up in your post:
Lost touch with your good friends from school and college - I thought this couldn't happen to your generation, so I was really surprised to read that, what with social media, dead easy to reconnect with them I would think
feeling like you have nothing to say - big problem for a shy person with a very set routine of work / sleep / TV. Need stuff to talk about which probably means getting new hobbies that you feel enthused about.
Money - you sound like you've got savings, but stress about dipping into them. The vast majority of people in the UK have barely anything saved so you are doing better than them. Give yourself some saving goals, realistic ones, and feel happier about spending the rest on the here and now. work to live, don't live to work
Motivation - you mention not wanting to do stuff a few times in your post - not going for a drink / not going to the gym / not wanting to game. Kind of classic lethargy from being down. I find I'm much more likely to get to the gym if I have a class booked, or a training session with a buddy lined up. Don't know if that's possible at your gym, but worth finding out. Being fitter gives you a lift
Try new stuff - new hobbies give you a reason not to sit at home watching tv, widen your circle of friends and give you more to talk about. I always recommend climbing at this point, don't need a friend but will end up in a social environment. But really just try lots of stuff til you find something that works for you. You'll slowly get that wider circle of friends
Gaming - you do realise if you had posted this 6 months ago you would have had 20 replies saying get Destiny and play with us. Next time the forum gets into a MP game get it and join in with us man, you'll be more than welcome.
Socialising - next time you get invited out, just go. Be the driver if you don't want to drink, but just do it. I'll probably get shouted at by all the recovering alcoholics, but having a couple of beers with some mates ain't going to hurt.
Anyway enough from me, I hope some of what people have said helps.