Dont know what to do... help...

Hello, im a 21 year old girl who has a perfect life, boyfriend, loving family, good job, then 3 weeks ago my mum left my dad after 30 years of marriage in £180,000 worth of debt. As you can imagine myself, my 2 younger brothers and my dad were devasted. The next day she decided to tell us why she'd left, she was a lesbian, i couldnt believe it, felt sick to the stomach. I wanted to know more, so i spoke to her in which she said she'd met a women and had "kissed her". To cut a very long story short we then found out she had an 18month affair whilst going through fertility treatment to concieve me, with another women in which she ended this 2 weeks before i was born, no-one had ever known about this and we were deeply shocked. I met the women when i was 12 as she was a part of our lives as family friends. I dont know how to deal with this, i feel like my whole life is a lie and that my world has fallen apart. She has now moved back in with my dad, he is totally indenial and doesnt consider it an affair and says he doesnt care that she doesnt wanna be with him like that. They are pretending to be this big happy family when my mum is a lesbian and is pretending to people outside the family she is a straight women. Im finding it so hard to deal with all the lies and hurt she has caused and i cant pretend to be apart of this "happy family" as i feel all this was caused by lying. I really just dont know what to do as regards my relationship with my mum, we were very close before all this and i feel like i have got to know/bond with someone who was pretending to be with someone else and just feel like my whole life has been a lie. If anyone would like to give me some advice or anythin it would be greatly appreciated.

You could always try to talk to your mom about it.
Talking is always a good thing to make you feel a bit better.

Tell her how you feel and what you think about it all.

This must be a very difficult time for you, but talking to your Mum about it is the best thing to do, she probably and most certainly doesn't want to upset you, we all have feelings that we can't change so you shouldn't feel bad towards her, just talk to her, tell her how you feel and maybe you could work it out, talk to your dad too, sit down together and tell them your thoughts and feelings, just ignoring the problem and feeling down about it doesn't help at all.