My girlfriend and I are have big problems in our relationship due to lack of or no trust at all. My girlfriend is feeling very insecure and emotionally unsafe with me, to the point of losing all trust in me because of things that I've said and done.
I told her about things that I had done in my past...for example...

When I was younger, I had kissed my friend's girlfriend, nothing eventuated from that kiss, it was just one of those things, but this left my girlfriend with doubts of whether this could or would happen again or if I'm capable of being faithful within our relationship.
I told her how I used to be the only male that lived in a flat with all these other women. Nothing happened between any of the girls and I, but my girlfriend has doubts because I was capable of kissing someone else's girlfriend.
I told her about sleeping with two sisters, on separate occassions unbeknown to me at the time, and because my girlfriend has sisters, she is now doubtful in this area also.
I told her how I had had a sexual relationship only, that had no emotional bond or ties. This went on for a time with another woman and this has left my girlfriend doubting my ability to commit emotionally to her and our relationship.
I accidently sent her a text message that was meant for another women. That was before we became partners, but nonetheless it has left her with doubts now, wondering if she is the only woman in our relationship, or is there someone else that is hidden away from her.

Since I've been with her, these are the things that I've done

I used to constantly tell her how great other women looked, I paid great attention to detail and I would tell her all the parts about them that I found of interest, not thinking that these comments were hurting her and these comments were pushing her away.
I would watch a programme / video / movie etc and whenever a great looking woman was on, I would make noises of approval and she would hear me, now she doesn't like to be around me when I'm watching any programme due to fear of my noises and pushing her away a little further.
I even sent her a detailed text message of a sexual fantasy that I'd envisioned with another woman, once again not thinking about the effects it was having on her. This is where the trust within our relationship started to crumble.
I would constantly be in contact with her for any and every reason and chance I had, and then I would disappear for hours without any communication with her.
I did this several times, and my reasoning always came too late.
Unbeknown to me, she would be at home thinking the worst of me in my absence.
These blank spaces of time and no communication, broke what little bit of trust she had left in me
My girlfriend tried to talk to me, when these different problems arose, but I would shrug it all off, with some minor non-responsive comment and then I would forget about it, ignore the problem as if it was dealt with and finished. I change the subject, do anything just to avoid topic of concern for her.
I thought that given time, I would be able to fix things, but it didn't and I couldn't fix it, because I don't have the answers.

All this took its toll on my girlfriend and she left me.

I love my girlfriend very much and I want her back.
I want to deal with my issues, I just don't know where to start, or what to do.

If there is any way that you are able to help me with my problems, I would be very grateful and appreciate any advice that you may have to offer.