Ok, here it is... I have a beautiful 10 week relationship with a girl that I fell in love with. She loves me a lot and she cares a lot. I mean really a lot. We have done so much in those 10 weeks then other people, and myself in past, didn't do in few years.
It is like we know each other for 10 years.

But here what went wrong:
During our relationship I was receiving a lot of calls form my ex-girlfriend (6 year relationship), and been stupid enough to answer them.
Because I am OK with her, can talk to her about stuff. Also I have received a few text messages. Thing is, my cousin also was calling me from same phone few times. When my girl asked who's calling I said my cousin almost all the time. I thought I was protecting her from my past life in some way…STUPID fckn idiot. She is now mad at me when she found out what's going on and I told her. I have not been 100% honest, and that is the thing she hates the most. She said that she doesn't know what to do now, she is broken, and that she loves me a lot, and cares a lot, and it's not a problem to see each other and talk, but she lost confidence and trust in me.

She said: If you want to solve this problem and make things normal again, I am here for it, but I don't know how can you do that.
She is so sad, crying, not leaving house except for work… I know that she loves me and that she want to spend the rest of her life with me, but she doesn't know how after this. I just want to make things right I mean…it is a stupid, stupid thing that happened, was happening,…I love her a lot, and I really want to regain her trust again. I really want to make things right. Also my cousin made a call that I didn't know about, until today. She called my girlfriend and told her that is not my fault for being so OK with everyone and answering calls, and stuff, and that she was using same number from time to time to call me and see what's up.

I am sorry for making this text so randomized, I am under a lot of stress and I need your opinion on this.
What should I do?

How long has it been that she got mad about your lying? That's bad in only 10 months of knowing some one. For now let her cool off, have time to think, and talk about it. After a sincere apology. Trust and confidence can only be gained through actions, over time, so basically, you are starting over and you better have learned a lesson in the future.

As bad as you think your past was, you should not have lied. But don't panic, let the dust settle and do better. See what happens in a week and make the most of a second chance. And tell your cousin you will no longer take calls from the exes number.