I tried googling but all I got was crap about hormones and mice.
Hormones, mice, and purple chickens. Sounds like a chemistry experiment.
Sounds like you're getting a bit
farouche (a French word meaning simultaneously wild, sullen, and shy, like a wild animal not used to human contact)
I agree with what everyone else has said thus far. I particularly like CzeCze's concrete suggestions for getting out and being around people, even if still at a distance. Here's another one:
If you're in school, then pay attention to how others contribute in class. At the end of class, when everyone is gathering their books to leave the room, go up to someone and compliment them on something they contributed: "Hey, I like what you said about monarchy vs. democracy--that was a real good point." You don't have to get in a conversation; just give them your compliment and then be on your way. If you can't compliment them right after class, then usually anytime in the next 24 hours is usually fine for a small compliment like that.
It's like the rep system. You drop them a little "Attaboy," but you do it in a way that doesn't require or expect further interaction. Most people like those little unexpected "Attaboys"; those who don't like them can't fault you or make an issue out of it. Meantime, you get a little positive buzz out of paying notice to other people and giving them some credit when they're looking good.
And who knows. One day a little conversation will arise at some point. It needn't be a long, deep chat. Just build small bridges to other people on a regular basis, and get in the habit of being around people without getting stressed and putting up your defenses.
Another suggestion: Take a recreational class or join a recreational club (square dancing, line dancing, camera club, parachuting classes, whatever). You'll be around people, and you won't have to question their motives for being in your company. Don't forget to interact with them lightly and give them an "Attaboy" when they do something well.
Then when I'm told by someone I am in fact liked, I think they're lying and keeping me around for some sick amusement. I still hang with them because it's either that or being isolated by myself.
No need to pick apart the various motives people have for hanging around each other. When I was living in the barracks in the military, the reason I hung out with some people was obvious: They were bored, and I was lonely. And it was a perfectly good basis for a friendship--one of the best, in fact. There's nothing wrong with wanting to be around other people to alleviate boredom or loneliness. And since we had nothing in common, I ended up hanging around with people I would normally never have considered as friends. They exposed me to new experiences that I wouldn't have sought by myself; some genuinely interesting friendships arose across time. Serendipity and all that.
Don't look for deep reasons to be in the company of others. Most people don't require a big, deep connection or rationale to be friends. They're just bored and looking for someone to help shake them out of their lethargy for the moment.
If you're severely depressed and someone offers to do something with you, it doesn't necessarily mean they pity you and want to help you out. More likely, they're just bored and need some company. Depressed people can be good company--they're relatively low maintenance, and with their griping they sometimes open up more than they think and provide some dark humor and/or interesting new views on the world. Of course, depressed people are also monotonous over time and eventually turn boring and uninteresting; friendships don't last long with depressed people. But that's okay--not everything has to be deep and long-term. Nothing wrong with having a few laughs together and then going your separate ways.
Accept things as they appear on the surface and quit picking things apart looking for ulterior motives or deeper meaning. Most people aren't that deep.
If someone offers to do something with you, go for it. Have some fun for an evening and don't worry about motives or how long the friendship will last. Live in the moment. Conversely, if you're bored and you see someone else looking bored or depressed, then invite them to do something--have a coffee, play a game of checkers, go get a burger, whatever. Don't create any expectations beyond the moment. Just alleviate your boredom in someone else's company, and then tomorrow you can evaluate the experience and see if you want to do it again with that person.
If you can capture that "Live in the moment" attitude, it will help you understand the world better. You'll see that people aren't usually deep and don't usually have ulterior motives. They're just bored. And that's not a bad thing. There's an infinite supply of bored people around you, so there's always things to do and people to meet. Live your life in their company, and after a while you'll find that you're encountering a lot of variety, doing a lot of things, and having a lot of adventures. Not a bad way to go.
And then occasionally you'll encounter someone with whom you'll share a deeper connection. Fine. But don't forget to live in the moment with the others as well. They're the ones who will keep things light and fun and expose you to some new experiences and perspectives. Novelty is important--it shakes you up a bit. It keeps you from getting stale and old before your time.
Just my own spin on things, of course. Take what works for you and don't worry about the rest.