losing grip on reality

i feel like a genuine battle in my head about if i’m dealing with someone who is altering my reality (partner for context which i know changes the severity of this) or if it’s just genuinely all on my head.. there has been on record times hes lied to my face, or purposely made me feel bad. but recently i find myself crashing over small things. asking for support/ reassurance in a certain topic or action, and then when we have those deep talks i genuinely cannot tell if hes being real or not. i cant tell if im overreacting, or if im justified in my emotions and lash out. of course i shouldnt lash out,, but i bottle up everything until then. i dont know im trying to be vague as to not let my emotions drown out my real question

how can you tell if something malicious is genuinely happening or if your bpd brain is making something worse than it actually is due to spiked emotions