Girlfriend might be lying about being raped...Help!

Hate to have to bring this up but there is a surprisingly limited amount of information online about the situation ive been drawn into.
So heres the story: Ive been seeing my girlfriend lets call her Lexi 24y/o f, and I myself am a 27y/o m for just about a year now. Last night we got into a argument around 12:00am about a topic we were tense about all day. Please do not judge but we were staying in a lower / middle range motel that we stay at pretty often and are both addicted to opiates even though thats pretty irrelevant in my personal opinion.
She has been raped twice that i know of in the past , one of the attackers was prosecuted and convicted, im unsure about the other.
Weve argued before about her being out alone late night as there are some weirdos in the area and she has a habit of taking flight instead of talking out any issues, shes also cheated on me before and told other minor lies that diminished my level of trust but still i feel like i should give her the benefit of the doubt and provide her with as much comfort as possible for i could not begin to imagine the aftermath a rape could have on someone.
So after she walked out the door i could hear her chatting with a couple males one or two rooms down, sounded as if there may of been a female also. Could vaguely hear their voices and couldnt make out any of the conversation.
I know most people will think i should of interfered right then but understand i was pissed at this point because i just got done telling her how much that bothers me to be walked out on. Im not abusive or irrational and rarely yell. Im pretty easy to talk to so that really is insulting to me.
After about ten minutes the voices leave and i hear a door close, not sure if she went inside also or ventured elsewhere but again out of my frustration blew it off.
45 Minutes later im really frustrated and decide to walk to the store and see if i bump into her along the way. About ten feet out the door i see her walking towards me from the other side of the street (appeared to of maybe just started walking towards me when i came outside and may of been sitting for a few minutes). She was distraught in tears, pants were buttoned (jeans) but i could see her panties hanging out from the top still worn but ripped on one side, her shirt was also ripped , and the only thing i could maybe consider to be a sign of struggle other then the clothing tears was a small amount of blood on her face (easily.could of been self inflicted from a pimple or something). And another thing to consider is she is into some pretty rough sex (as am I so was already experienced and happy to accomodate) retraints, spanking, choking, bdsm type stuff which i know can be common in victims of previous sexual assaults so end up defending her in that field also
Im freaking out asking what happened and where he was , which way did he go? She proceeds back into the room without any response to lay in bed while i ran around the nearby streets looking for anyone suspicious or any witnesses, its a pretty busy street in a mid size city and even being late theres still a handful of people on foot and a little vehicle traffic. Had no luck......and figures mysellf being in a motel across the streetf or SOMEONE would hear or notice had this happened somewhere public which may or may not be true as she still has remained silent about it and i dont want to make her feel like i think shes lying or think its her own fault.
When i got back from checking around outside she was still in bed and proceeded to the shower without making any police or hospital contact (even though she contacted authorities in the past).

Is there any tell tale signs i should be looking for, non invasive questions i should ask to help me determine the truth and comfort her should this be the real deal? This is the last straw for me if it ends up being bullshit just want to make the right choice. And get some unbiased opinions.
I know its a long thread so if you managed to read through and better yet can shed some light then thanks in advance!