Jeez man, you might want to format this thing if you actually expect replies.
"I just realized once I actually get out of this place where I'm locked it's gonna take me quite a fucking while to be as normal as I am "supposed" to be"
Where is "here"?
"I have this certain idea of how I am supposed to be, of who I am supposed to be and of how I am supposed to act"
What good will conforming to this do you? Why not find a comfortable midground between you and that so that you simply appear quirky while under less pressure?
"the way I currently am is no good for what I wish to achieve, I aim to be succesful, to not seem weird or hateful to people even though I actually am"
Depending on which field, seeming "weird" can actually work in your favor.
"I have been kept away from society for a very long time and I still have 4 months to a year more to remain this way"
...are you typing this from an asylum or something?
"locked in my room with my only social gateway being the internet..."
Sounds like Sinister's wet dream.
"I feel like this has changed me more than it was supposed to, I feel like I must forcibly fake being normal when I talk to people unlike how I was before"
So... you're just out of practice? Be willing to make mistakes and it'll start feeling natural again. Speaking as someone who occasionally takes breaks from "people" as a whole, it's not too hard to bring it back if you don't criticize yourself too much. The worry is often what's sabotaging things more than anything else.
"i used to simply act a certain way and not feel too weird about it but now it's not exactly the same,"
So why not try to be something closer to yourself with some boundaries established instead of trying to be another person entirely? Basic manners can be enough on their own, and being another person will mean building a social life around yourself that holds you to that expectation. If you be yourself instead from the getgo, they'll expect only that.
"it got to the point where I feel sick to my stomach when I'm talking to people"
That sounds like fear. Tums can help with that, as can avoiding foods with high acid contents. Otherwise not worrying about what other people think of you as much will make you appear less socially awkward.
"not everyone though this only happens with those that I see as normal, outgoing and social"
So go for abnormal company then. At the very least they'll be good practice for your confidence while they'll likely be a bit more accepting of your quirks and flaws. I prefer abnormal company personally, as "normals" (in the sense of trying to be normal) are just so... boring and typical in their aspirations.
"i feel perfectly comfortable talking to those i can see myself in, but the ones I don't.. they completely weird me out..."
Ever try letting them know that to create enough peer pressure to shift them towards your way of being instead?
"And it's just through not, i can't even begin to imagine how it's gonna be in person, I imagine it to be exhausting..."
..."normals" make you feel uncomfortable over the computer? Really?
Weird.
"Not that nothing is exhausting anymore... I have been overthinking this for a very long time"
Overthinking indeed. Loosen up, or said overthought might cripple you.
"and even though I have some people I talk to from time to time, i see no one that is there for me to vent to"
If you be yourself and draw in others who compliment that, you'll have a wide base of people to vent to who may even share your feelings on the matter. There's so many people out there, and when you really dig into who they are, almost no one qualifies as "normal", and personality is somewhat adaptable for them as well. They may find themselves becoming more like you if they find it to be a comfortable fit.
"there have been people for that but I just pushed them away because seeing how I was reliant on them made me feel weak.."
Because keeping it all inside makes you soooo much stronger. Venting's cool from time to time as long as you can trust who you're venting towards, and if you continue to seek out "normals", you'll likely find yourself silenced instead of venting towards a state of peace.
"that is not the subject however, I need someone to give me pinpoints on what to do exactly since I feel senseless"
Let yourself be able to look foolish. If people leave you over it, there's always more people to try on. They only matter as much as you allow them to matter, and worrying over it sounds like it's jinxing you worse than anything else. Some admire the bravery behind the willingness to make mistakes, myself included.
You sound like you're mostly out of practice. That's easy enough to remedy through, well, practicing.