Not sure where to go from here...

I'm honestly not sure where to start. I'm obviously new here... been reading for a few days and so much of what I read here sounds eerily familiar. That is enough to scare me. I'm not married, but engaged. My fiancee and I have been together for four years, living together for three. We are supposed to tie the knot this June.

Where we are now, is an ugly place. I have lost a lot of trust for my wife-to-be. I guess I'm here to find out if it's justified, or if I'm just an overreactive man. Let me preface this by saying that I love her with all that I have, and would do anything (and have done plenty of things that most men wouldn't) for her. We were even homeless for a little while... I stuck with her through that, no complaints, just love. Not that it's immediately relevant, but now we are financially stable and comfortable. Anyway... here's my story.

For the entire duration that I've known her, my wife-to-be, we will call her "M," has been physically attached to her cellphone. At first I thought nothing of it, until I noticed that guys were calling and texting her in the middle of the night. She said that she has no control over what they do... fair enough, point taken. While it still bothered me, I did my best to bury it and let it be. About a year and a half ago, when we were really hard up, we made a running joke that she should get a sugar daddy so we could make ends meet. With my consent (what was I smoking?) she joined a sugar daddy/baby meeting website, and actually ended up talking to some of them. I was ambivalent.. but thought hey, it's harmless. Finally, she started exchanging pictures with one of them, and getting extremely flirtatious in the messages... that's when I couldn't take it. It made me violently ill, and I kept playing the messages over and over in my head. She pledged to stop, that she couldn't see me hurt like this, and it did.

After that, I think everyone on this forum would understand that I became snoopy. To be fair, I've always been a little bit of the "watch over my shoulder" type, probably because of the amount of times I've seen my parents talk about divorce and my mom getting emotionally involved with guys over the Internet. I started sifting through e-mails, Facebook, anything I could find. Sure enough, she has been texting this guy in California off and on for years -- we will call him "J." I asked her to stop, because I felt it was inappropriate and it made me feel uncomfortable, and she claimed that I was controlling her, didn't trust her (true at the time), and was plain livid with me.

About a year ago, things got pretty heavy with this J character. M was texting him literally all the days, all the times. From what I saw they didn't exchange pictures... but they definitely said some inappropriate things. She wished he was in the shower with her, she was single, etc. Enough to break my heart. When I confronted her, instead of addressing the issue, she blasted me for sifting through her phone, and subsequently put a lock on it -- which, in turn, made me MORE suspicious. (She claimed it meant nothing, it was a big joke -- if it was a big joke, why is it now a secret?) From what I could tell, though, it cooled off after I confronted her.

I realize I do sound horribly untrusting. I can live with that for now.

Let's fast forward to yesterday. It had been a serious length of time since I had done any snooping.. I thought we really had a good handle on everything and things were smooth. We recently got a cellphone plan together, so I went to see what the usage was like. I find out she's been calling not one, but two guys in California for some pretty hefty lengths of time -- all right before I come home from work. The rest of the time, she's texting them. I decide to snoop... in her email, she's talking to a third guy, where she is obviously flirting. At least this time she didn't say she was single -- but did say that I wasn't the "best lay," that I was "bland," and that she "needed something more."

While obviously it wasn't the best option, I blasted her by text message -- sent her a photo of the email. Basically told her that she had been lying to me, that I KNEW she had been lying to me, and that I didn't even know what to say. (Although say lots, I did. Perhaps too much.)

Her reaction was this... that she had something she needed to talk to me about for a long time, but never knew how. She said she was scared to marry me, afraid of the pressures of "forever" and being expected to be "perfect." I told her that if she lied to me ever again, even by omission, that I was done. She called me on her lunch from work to try to explain, and I told her how I felt -- how all of this deception makes me feel, how it makes me question her every move. It then got turned on me, about how everything is always about me. The problem here is that she doesn't know how / like to / want to communicate with ME. She even told me point blank on the phone -- point blank -- that sometimes she just doesn't want to talk to me. She didn't offer a reason. I asked her what made her talk to me this time, and she said "you've never said you were going to leave me before." (This is something she has threatened several times. I have begged her to stay every time.)

We didn't get to talk about it when she got home (per her request, AND we have a friend staying over for a few nights)... I'm at a loss. Please, please, offer any and all advice. Can I trust her? Should I? I don't even know what to think anymore. I am devastated.