for me I know it's getting bad again when the intrusive thoughts become more frequent, suicidal thoughts surface and become scarier than the usual jokes, my mood drops faster, it's hard to focus, getting out of bed becomes a chore, and it becomes hard to name a single good thing that happened that day. it can all vary person to person, but these are the signs I look for in myself to seek help from my therapist:)

It can be sneaky sometimes. You won’t even feel depressed but it might be really hard to do basic things like shower or sleep, or maybe you sleep or eat too much! Step back and observe how you respond to things. A big indicator, at least for me, is when I start to isolate unknowingly and stop doing things I like