i think im mentally ill

okay so im not sure now if im going crazy. a couple of months ago(i moved to my dads oct 1st) before i moved to my dads i lived with my mum...and she brought a man into our home who was her boyfriend so okay it was around july 2021 and it was going alright. then the start of march the abuse started he would hit my mum apparently and i didnt see it i heard it and their screamings and him threating my mum. he threated me once, walked on me showering three or two times and my mum use to call me names sometimes but i understand shes messed up in the head because of him. my nana on my mums side doesnt believe me that he hits my mum. i heard it, i heard her scream. HEARD THE HITS AND HIM THREATING TO HIT HER AND THEY DONT BELEIVE ME AND NOW HERE I AM STUCK MENTALLY ILL AND WANTING TO COMMIT