(...Continuing)

Thought loops and spirals are more difficult to distinguish though and having no experience of OCD, it's kinda above my pay grade but an autistic person is going to have positive, negative, and neutral thought loops whereas with OCD thought loops we could take harm OCD as an example - a person with harm OCD might experience a battleground in their own mind whenever they pick up a knife and someone else is around. They don't want to hurt the other person. They have no intention of hurting the other person. The idea of hurting them is distressing to them. Yet despite all of that they might deal with really intense, persistent, and distressing thoughts about harming that other person every time they touch a knife and they can't just "move on" from thoughts and visualisations of them doing it.

Then for stimming, it's pretty simple - it should feel soothing and comforting or as a way of expending nervous energy. That sort of thing. It's repetitive behaviours that are generally non-harmful (behaviours like drawing on a cigarette or picking your skin would beg to differ here) which you have a strong preference for doing. They should be associated with feeling better and they help you regulate your nervous system. You should generally be able to opt for when you engage in stimming behaviours and typically you should be able to cease the behaviour without it intruding on your day-to-day life.

For example if you touch something with a gross texture, you're probably going to shake your hands. This is actually a really common form of stimming seen across all people and it even extends to animals too. Behaviours like this can look like OCD because it's this pattern of stimulus and response that plays out every time but the difference is that you don't feel bad for shaking your hands, you want to shake your hands, there isn't any particular psychological investment in the behaviour, and you could suppress shaking your hands and it you won't feel like the world is going to end or get intrusive thoughts about how the next time you hop in a car you're going to have a car crash because because you didn't shake your hands this time, that sort of thing.

There's a caveat here in that if you are already overwhelmed or overstimulated and you're at your limit then you might feel a compulsion to stim to help regulate yourself and attempting to suppress the stimming causes a meltdown or shutdown. The difference here is that the things aren't directly connected in your mind, the urge is different, and you can redirect stims whereas I think that OCD behaviours can't really be redirected; if I'm really emotionally distressed, I will engage in self-soothing behaviours to help me cope with the distress and if I don't stim/if I stop stimming then I will become a mess but I can probably choose from a range of stimming behaviours that soothe me so I'll pick whichever is the most effective and appropriate one for the situation. For an OCD person, if one of your behaviours is switching lights on and off a certain amount of times then as far as I'm aware you can't reason with yourself and settle for turning the screen on your phone on and off or doing the same with your TV - it has to be the light switch and there's no compromising on that. Doing otherwise will be the cause of emotional distress whereas an autistic person might find it really soothing to flick a light switch so they'll do that to relieve distress which comes from elsewhere in their life.

Usually if it's a repetitive behaviour as a response to feeling bad, that's probably stimming. If it's a repetitive behaviour that must be done or otherwise not doing so will directly cause you feel bad, that's probably OCD. It can be a fine distinction to make sometimes but that's probably the easiest rule to use here.

I'm not a doctor, not a lawyer, not an expert, and not a person who experiences OCD so take it all of this with a pinch of salt.

Sorry for the long ramble. I hope this has helped make sense of the distinctions between the two.