You do not have to do anything you do not want to do. Really.
You get to choose. If you do not want to have a shower or girls' night out or any of that stuff, tell people that you do not want it, that the thought of doing that gives you anxiety and makes you upset, and it makes you very sad and will not be happy in the least to be pressured into having one.
It is possible to say this stuff plainly and politely; you just have to be firm and thank them for the thought, but tell them that the whole shower thing is not you and you absolutely would be sad and uncomfortable having one, so thanks for the thought, but no, you will not be doing that.
But continuing to allow your relatives to pressure you, you are giving them the impression that they have a say in what you decide to do. This is wrong, and you should shut it down ASAP. So the next time anyone contacts you regarding what you should be doing, tell them that you are perfectly happy with your decision, you will not be doing "X" and there is nothing more to discuss about it. And change the subject. Do not get drawn into defending your choice - it is YOUR CHOICE and they do not have the right to keep picking at you until you change your mind. Shut them down. "Aunt K, I already said I am not going to any shower in my honor. I don't need or want one at all. I'm not discussing this any more, so please stop bring it up. Thanks for understanding."
It is you and your intended that are getting married - not your mother, not your aunts or cousins or grandparents. If the person that is pressuring you wants to have a shower, then tell them that they are welcome to do so for their own wedding... but you do not want one. And if friends/family are texting/calling/emailing you to badger and pressure you, then ignore their contact until after the wedding. You don't have to acknowledge their rudeness in trying to make you do something you do not want to do if you've already explained to them your preferences. Ignore, and distance yourself if they can't let you alone about this.
And then move on, and do not dwell on what others want. Because that is the essential part of this. State what you want and will be happy with - plainly and without any chance of misunderstandings, and then don't give that stuff any more space in your head.
But if it was me, I probably would just avoid the reception thing as well... have your small intimate wedding with just close family present and then save the money you'd have spent on extended family reception and just have a nice get-together like a potluck or BBQ at your house or a local park without calling it a reception or otherwise mentioning your wedding stuff. Then it's just a family reunion where everyone can discuss family stuff and get caught up on who got married (!), who is expecting, who got a new job, who moved... and take the focus off of how you had a non-traditional wedding.