I can’t

It's okay, take them in order, first there's the obsession and after that there's the compulsion. The compulsion is the response to a certain obsession. (ie. You feel like you are still contaminated after washing your hands so you wash them again, the obsession is the contamination while the compulsion would be washing your hands). Ofc, there's times where the compulsion is not so visible like a mental compulsion. It's definitely hard for me too, I sometimes think I'm actually avoiding doing a compulsion and then realise I actually did a compulsion instead of avoiding one. It can get tough and it takes time, don't beat yourself up too much about it and don't try and figure it out all the time, eventually it gets repetitive and you kinda see what the compulsion actually.

You aren't alone. I think the problem there is trying to differentiate them; that would be rumination. if it feels like you urgently have to solve this and need an answer, it is OCD. I know it is so hard, but you will get through this

Obsession➡️something you fear, a situation you think that might've happened or will happen, or it can be anything you fear. For example, obsession with the fear of harming someone, or the fear of dying. Rumination ➡️ is the analysis you do when you have an obsession. Did I hurt them? Will I die? Did I wash my hands correctly? Oh no I didn't clean with chlorine so something wrong will happen" all those thoughts count as rumination, they are analysis revolving your fears. Compulsion➡️ action you do to calm the fear of your obsession being true, or to calm the anxiety while ruminating. These actions are to reassure the anxiety immediately and the calm is short term, just like the joy after eating sugar, so, it is addictive and repetitive, like asking things you already know, checking things you already checked, or, making these actions for the first time but knowing you want an instant anxiety relief. Hope this helps

For me, almost any thought that comes after the initial thought is rumination and is too much attention towards the original thought. The original thought happens in a split second.

Rumination is a type of compulsion. Say moral questioning. You got a thought in your head, you might have a straight away answer. For me, I don’t. I doubt. So it makes me think. And think. Which is ruminating. I want to know the answer (the anxiety) so I ruminate (the compulsion) to try to figure it out.

Like for my the intrusive thoughts are always there so I don’t know when the rumination begins. They are so similar to me in my mind

Like the rumination is intrusive itself

I have sometimes found myself deep in rumination without realizing what the obsession was that started it. Periodically, I like to ask "is there a 'what if' that is driving what I am currently thinking about?" If I can answer this question with a yes then I can identify the obsession: e.g. "what if I did something wrong/touched something dirty/hurt someone/etc." Then I find that it becomes clearer that I was in fact ruminating, and the cause of the rumination was to answer the obsession.