How am I going to be fined?

I did something silly again! 😭 I take the train regularly, and since there are no barriers where I board, I’ve sometimes genuinely forgotten to buy a ticket. I ended up paying fines three times last year and today I was stopped again but this time I was told it might go to court instead of just a fine.
I’m really anxious as I’ve never intended to avoid paying, but I understand how it looks. I’m also worried about the financial impact as I’m already managing tightly in London or worse- a criminal record.
I’d appreciate some advice please! Not sure how this is going to be dealt? This is for Southeastern