My girlfriend is in relationship with some guy for 4 years, and we started going around for 1 year, recently I found out about her relationship. She never said about that guy instead she said he is her brother, and interestingly she also says that she loves me. Even I love her and I do not want to loose her that is why I never revealed that I know all about her, but from inside I am very depressed but I never let her know that I am depressed whenever we talk. I do not know what to do?

Talk to her. Let her know how you feel. How do you know for sure that she is lying?

If you know for sure about the lies then you need to be upfront with her instead of keeping everything inside.

Also decide whether it is worth continuing this relationship. Especially if she is in another one at the same time.

Too many questions need answering, right?

It would help your depression I feel to do something about this liar in your life. Like getting rid of her.

Giving your heart to a liar cheater and deceiver can't be good for you, can it?

To be straight , she obviously can't let go completely with her ex , you should talk to her! This could eventually all go away and her feelings get stronger for you but it could go the other way and you get heartbroken , I personally would want to be with someone that is committed to me and doesn't have to lie.