OP you are quite similar to me. I work, I don't have agoraphobia, have no idea about my fertility and haven't been diagnosed with and ASD (though some people have been suspicious), but apart from that a lot of what you say is similar to me.
A couple of days ago I just wanted to die as I felt so in pain from feeling lonely and isolated. Some posters here on Chat were extremely kind and helped me through. I still feel absolutely shit but a bit more stable. Don't hesitate to post on MN if you need someone to listen - chances are there will be many who know exactly how you feel, who have been there and care about you feeling better.
I also contacted the Samaritans by email - it's helpful. It's slow, so if you have the courage to call instead it's probably better.
I find it very, very difficult to meet people. it has improved over time but I still can't get close to people however much I try. I used to have crippling shyness - I once went to join a volunteer group and stood outside the door because I was too petrified to go in. Now I am a lot more confident and can manage the basics of meeting people. But it's still really hard as i feel I have got to the point in life where everyone is pretty much set in their ways and not looking for friends or partners at the moment. It's horrible. I
I was a virgin until I was 22.5, not much younger than you are now. I haven't had a proper boyfriend ever, it makes me feel like such a freak. I have tried internet dating and wouldn't recommend it if you are feeling a bit fragile, it can be brutal if you are not feeling thick skinned.
I also love cakes and cats . If getting your own cat could be tough with vet bills etc, could you perhaps volunteer to help out with Cats Protection or a similar organisation? My local cat shelter organisations are always looking for people to foster cats, or you could help out at re-homing days or fundraisng events or something like that if and when you feel up to it. You get to meet lots of lovely kitties that way and people, but they are less fun . Having a cat at home for company is wonderful though - if you could manage that it would be a great idea.
Re cakes - I've done a couple of enthusiast courses which are fun but expensive. I would love to do a proper semi-pro one but they'd bankrupt me. I don't know how skilled you are, but if you are beginner-ish you could do what I do and just watch loads of youtube videos and practise skills from that.
The one thing that has really improved things for me, which some other posers have mentioned, is exercise. I used to be really inactive and am the least sporty person ever, but now I do fairly hardcore exercise for 5 or 6 hours a week. It helps clear my head, gives me something to improve upon, it gives me an hour or two away from the monstrous feelings of inadequacy that I have most of the time. It's also made me fairly fit, which I never was before, and my eating disorder has improved a little. The main thing is it is a type of exercise that I absolutely adore - I had a gym membership on and off for a while but never went because it was boring for me. Could you find something that you might like - perhaps yoga, running, dance, cycling? You can start off cheaply - a cheap bike, instruction DVDs or online videos for something like yoga or dance, running or walking which are totally free... and then when things improve, perhaps when you get work and a stable income, you can step it up.