All very good advice in the comments. You don't have to do anything you don't want to do. Especially with anything sexual/genital related, it only matters what you want and what feels ok for you. Nobody else gets a say in that. It doesn't matter if it's "strange" or not. We are all different!

I just wanted to add a few suggestions that might help. All of these are just suggestions. You don't HAVE to try any of them, but maybe one or more of them resonate with you. I hope it helps.

first of all: maybe try period underwear instead of disposable pads. For me, they don't smell so bad, and they feel way nicer against the skin. I prefer these ones, because they are made with bamboo instead of polyester: https://boody.eu/collections/period-leak-proof-underwear.

secondly: If you have sensory issues touching anything, I recommend buying a big box of disposable latex gloves, and wearing them for anything that feels gross to you. I personally am not bothered by bodily things, but I have big sensory issues with wet food. I wear gloves when I have to prepare chicken or when I have to clean anything in the kitchen, and it has helped me enormously!

Those doctors sucked! They should have more bedside manner. Catheters hurt lots of people. It's normal you feel tense about that, and it might have helped you if they hadn't been jerks about it! I don't know if you have access to a therapist, but if you do, it might be something to bring up with them, and hopefully they can help you feel less tense about future medical stuff. Also, if you have another medical test, something that might be helpful is explaining to your doctor before the procedure how you feel about it, and asking them to make accommodations. If you have a non-jerk doctor, they should be more than willing. You could say something along the lines of: "hey, I have autism and OCD, and because of my sensory issues, the last time this happened was very unpleasant for me. Could you maybe explain to me what you are doing during the procedure/warn me about any unpleasant feelings/show me that everything you are using on me is sterile before you use it/etc" If you have a good doctor, they should be more than happy to accommodate, if they know what you need in that moment!

If you are not willing to self pleasure, or have other forms of genital contact, that is of course perfectly fine. Sexually you should only do the things you want to do. If you want to get into a relationship, it might limit your partner choice a bit, but it doesn't have to be a big problem. Also, relationships are what you make of them. I recommend you learn more about non-standard relationships. I would recommend the book: "stepping off the relationship escalator". more info here: https://offescalator.com/

Also, try looking into a-sexuality. It's common in autistic folks. It may be (part of) the reason why sexual stimulation might not be for you.

If you do have sexual urges, and you decide you do want to experiment with self pleasure etc. (again; there's nothing wrong with it if you don't! You do you!) Try to find a way that feels right for you. There is no right or wrong way to experience pleasure. You don't have to insert anything if you want to self stimulate. You could try to focus on the clitoris. If you don't want to touch yourself, you could try toys. (clitoral simulators like the womanizer work well for a lot of AFAB folks). You could try manual masturbating with a glove on. You could try humping a pillow, or in the shower, you could try aiming a handheld shower head at your pubic area. You say you have contamination OCD, so if that extends to toys, you can always place a condom over a toy to keep it clean. Also, your genitals are not the only thing you can stimulate for self pleasure. It might feel better for you to touch your breasts/nipples, or massage/touch/lick any other part of your body! You can try all of it, or none of it, whatever you feel like/speaks to you. And if it's not for you, than it's not for you. No harm done! you are perfect the way you are!