I'm alone, 39, and living with my parents because my career fizzled out. I still manage to enjoy many simple pleasures in life despite the frustration of not having my own independence which I blame on this f****d up job market.
I don't have a girlfriend either, but at least I have my porn.
If I were to kill myself to, I wouldn't even have these simple pleasures since I'd be dead in the ground.
I guess my response to this is just considering why you really feel bad. Are you just 'lonely' or do you feel left out or that you're missing out on something other people are enjoying? I've thought about my own situation and I do sometimes think I'm missing out on a social experience, but do I honestly feel lonely? No. At worst, I feel bored.
If you are receptive to the idea, look up Buddhism in reference to Desire and really consider if Desire is leading you down a bad path for a weak reason. Maybe your life feels strangely solitary, you see many people around you that are not this way. You desire to be like them, but feel unable to attain it. I don't think this is reason enough to consider killing yourself and many other options are available.