my girlfriend lied abt her previous sexual relationship with a guy.do I trust her.wat u think

I'm a guy aged 25 and my gf is 3 yrs older than me.i have a serious relationship with her for past 2 yrs and even at times we r planning to get married but I have serious doubts abt her previous relation with a guy and I think she is lying abt her so I don't trust her.so it started like this.it was love at first sight.i proposed to her and she replied me that she also loves me.at that time I asked her abt she having any previous relation.she said she is very close to a guy but she don't love her and are good frds.i agreed.within a week I visited her home and then I spotted this guy in het home.i asked and she said this guy has some family like relations with her family and he visits often and then also I agreed.so our relation is working very fine and after some time I have to move to other city for a period of 1 year.we have daily chats and even at times we have phone sex and its working very fine for us.i have still some doubts abt that guy so I asks sme questions and then one day she told me that this guy has one suded love for her for past 5 yrs since both were frm same college but she don't love him or have any feelings for him.we often talked abt sex and she is willing to have it the moment I come and she says shes a virgin so it will more fascinating to feel sex for first time.and the moment came when I visited her and we have sex but I feel her vagina is not as tight as it shud be for a virgin.even I have sex for time time as I'm a virgin too.but due to havingmedical backgrd u feel something suspicious.i talked abt this with her but she ignored and told me bcoz she is so wet that this cud be the reason.but I think she has some matured experienced kind of feel to her body and the way she behaves during sexual acts and she knows very wellhow to turn me on.how cud a virgin girl know so much abt sex withoutexperience.and mind u she is very horny during acts.
So this is where I started doubting her and her past.after 2-3 encounters with her im absolutely sure this girl is into sex.so the natural suspect was that guy whom she refuses to talk about much.so I keep pressing her about this guy and one day she started crying and confessed to me that this guy has fucked her forcibly 5-6 times in the past but she is not willing to.so heres my doubt u can forcibly **** a girl one time but hows it possible to be forced for sex 5-6 times.i asked where it happened she told meit was at the guys place.so here another doubt how can u force somebody into coming to his place and that too for 5-6 times its not possible its a lie I think.i don't have any probs with her past relations but its the lie that I think she is making of it is creating a serious trust deficit between us
Also upon some research I found frm my frds who knows her too that she is riding many times with this guy in his own car.wat I make of this.so there r some doubts I need to be cleared befire we move ahead.is she lying abt her sexual acts and just making a story of being forcibly fucked ? Is this girl in a serious relation with this guy? If she is serious qith hin why she lied? Why she accepted my proposal in the first place?.I also found that this guy is very poor and myself being frm a good background is she using me and dumped that guy? Also a question which is bothering me even more is as when we have sex first time her vagina seems a bit looseso was it possible that she is having sex with him when I'm for a year distanced frm her means she is ******* him and at the meantime sexing with me in the phone.so that means a clear cheating.is it possible that vagina streches more with having more continous sex bcoz now she seems more tight than our first time.plz answer this I have a very troubled relationship as all this things r bothering me.why she didn't tell me these things in the very beginning and acted so innocent