I'm in a similar boat regarding having all of your mates in relationships.
If you don't want to meet someone on the internet, consider meeting someone at a social group designed for an interest of yours (such as photography groups on meetup) or going by yourself to a bar or club. There's bound to be others there you could make friends with or girls/guys who are looking for someone too.
i always thought, you must be crazy or real lonely, to go alone to a bar or club... but now i just want to go out, and have some beer and talk with others. Also the weather is getting better and better...
I real miss the time, when i met my ex girlfriend, at first we were just friends at university, and i liked it, that she wanted to go out so often, grab a beer and chill at the green meadow, or some wine etc.
I loved it, because at the time (like now), my friends did all the boring stuff, to meet fridays, saturdays at friends home and play poker or something like that, and that everyweekend.
I whish, i could turn back the time...