she wants to end it after 3 years (long.) please help... so confused

So ive been dating this girl for nearly 3 yrs now. And things used to be good between us but about a month back we split up. we got into a huge fight about some stories her father made up about seeing me with my car full of girls out till 4 am... none of it was true .. so clearly this made me a little mad about being told that was what i was doing even tho it wasnt true.. so we split it off kind of as a mutual thing.. n then about 3-4 weeks went by and i was missing her like crazy.. i told her how i felt n that i loved her and only her and that i wanted her back. so we kept talking and hanging out starting to make things work.. we went back to telling eachother we love you and all that good stuff. but then after about 2 weeks of talking. her best friends boyfriend goes on to tell me that theres this kid she has been hanging out with everyday. and while we where split up she went to this kids familys house and spent the night.. ok so this clearly made things very different so i brought the situation up to her n she swears to me she doesnt like the kid, she has no feeling for him and that nothing has happen . and so on n so forth.. but it kept bothering me so i kept asking her questions, i know i mite have been pushy or repetative but i had to ask you know. i felt that if i kept asking her that she mite crack and tell me becuase she was single for a month anything could have happen.. and if something did happen we wouldnt be getting back together becuase im not like that.. so she swore on her mothers life and cried with me n promised me nothing happen.. so things where good for a few days.. we where having sex and stuff.. things where looking up n then yesterday i had a relapse and i kept thinking about this kid.. so i told her that she must kno if we get back together that he cant be apart of her life because it will make it hard on our relationship if she still is hanging out with this kid.. and she tells me she knew i was going to say that and move on.. so once again i let it bother me {im clearly insecure} so i told her that it was "trust" that was our issue n she flips out telling me nothing happen with this kid n that i have a choice to love her or leave her n she hangs up the phone on me.. so i think about things and i call her back about a half hr tell her that i love her n that i trust her and lets move forward from this because i just want to be with you..and ill do whatever it takes.. so when she picks up the phone she flips out on me n tell me she cant do this that i willl never change and that she isnt going to just drop her friends for me and she cant do this anymore its over for good.... i was crushed i called back to setlle our issues right then n there and move on but now she wants to end it because of my asking her so many questions about this kid.. but i mean how was i suppose to feel .. she was single for over a month anything could have happen.. and by the way people made it seem it was happening .. so i kept asking because i figured she might have just been hiding it to protect my feelings.. but knowing her like i do i now know nothing happen and i want to trust her but now she doesnt want to give me the chance.... please help me any advice?????

For one thing, whatever she did during the time you were split was NONE OF YOUR BUSINESS. You were broken up so it's not cheating. Both you and her were free to do whatever you wanted. Second, it was YOU who wanted her back. When you take someone back, there will always be a possiblity they were with someone or out dating.....you will go through this with every relationship you have.....it's a given. You need to grow up. Look at what your immature behaviour has done. It has ruined any chance of you being with her....I hope you have learned from this experience. If not, you will have to endure a future of more ruined experiences.

I'll be honest with you just let her go and move on, stuff prob happened between them anyways, but you kinda over reacted my giving such a negative behavior. Never jump the conclusions unless you're 100% sure she is cheating her staying over his house is suspicious, don't let her pull the love me or leave card on you just leave her and forget about her is she does care about you she will contact you.

What she did and with whom while you were broken up is neither here nor there. You were broken up. What is an issue (or would be for me) is that she continues to hang out with him one on one.

I'd just forget about being with her. It was the beginning of the end when you broke up the first time and she believed her father and not you. Not giving up a NEW friend who is a wedge because of him being in her life while you two were broken up is a red flag that I wouldn't ignore or stick around to be hurt further by.

Give yourself closure by texting or emailing her that you think she's right and like her, you can't do this anymore either and then go zero contact so you can heal from the breakup.