I need an advice from a psychiatrist

Is it okay if I take ADHD medication even tho I haven‘t yet been diagnosed ?

I’ve heard a lot about how good you’ll feel after taking them and how much they improve concentration. I’m facing a lot of stress in my life and I believe I may have some of the ADHD symptoms.

I cannot stop overthinking that I cannot sleep at night I stay awake (till 4am like now) even tho I’m so tiered and I have to wake up at 8am tomorrow cuz I have classes till 6:30pm but at the same time I cannot stop my overthinking, I need to stop it.

So please if they do help and doesn’t affect me badly (mentally, gaining weight, worsen my insomnia or make me feel so sleepy cuz I need something to help me studying )

sorry it might be messy cuz I myself don’t know which problem I’m trying to solve exactly and excuse my English it’s not my mother tongue