When will she trust me again?

[talltoe396]

I came across my gf on the internet.
The day I actually met her irl we kissed.
The day after that, I was sexual with my fb (for the last time).

I did it because I was not aware I was already in a relationship with my current gf.
I went on these kinds of dates before and in my (bad) experience, things could still go either way. Honestly, I didn't know what to expect. So I decided not to get my hopes up yet and change my life.

Anyway, I kept it secret for one year while staying friends with my former fb (who I had known for over 2,5 years). I was very afraid of telling my gf because I feared losing the greatest girl I ever met (which is my gf ofcourse).

Until one day my she found out, one year ago (together for 2 years now). After that, I broke off all contact with my friend.

Since then, she doesn't trust me at all and calls me a cheater and thinks I wouldn't tell her if I would cheat now.

At the time, my gf was 16 years old and she had kissed an above average amount of guys. She is now 18.

Telling her this doesn't work. The fact is I would never knowingly cheat on my gf. But I regret my actions so much. The thought of losing her tears me up!

What can I do?