You don't say how tall you are - actually you may have done, I haven't read all the thread yet - but if you are tall, you may be more statuesque than fat. Statuesque women are amazing and plenty of men would be interested. If you are a really nice, warm and fairly humourous person, I'm sure you'd have admirers.
However, being 15stone+ is not particularly healthy, I'm sure you'd agree with that. At the moment you're young and we all get away with stuff -eating too much, boozing even extreme dieting - when young but that doesn't last forever. You would feel better if you lost some weight, you don't have to go skinny.
I did that, blimey more than 20 years ago and when I put my mind to it, it was not difficult at all. I stopped being a couch potato (I did go to work but took little exercise), and comforting eating. Walked everywhere instead of going on a 'bus or car, walked up stairs rather than take a lift and had a little personal exercise regime, didn't take long, when on my own at home. Hee hee, it included my own version of ballet. The weight fell off! I felt marvellous too, I wasn't skinny but had a good figure. I did actually eat well and healthily. I'm just saying it is achievable but whatever you do, don't pressurise yourself.
I hope your new relationship goes well and wish you every success in the future.