Is AUTHOR wrong in the post ? POST : Maybe this is more appropriate for /r/relationships or /r/sex but whatever.

So i've been with my girlfriend for just over a year now, it's been by far the best relationship of my life in terms of being in love, stress free, sharing interests, sex life etc it's been a total unicorn relationship.

Anyway, I have only had two partners before her, both LTR. I'm personally against casual sex and drug use although i'm fine for other people to do it, it's just not the lifestyle i've ever wanted. She's said she agreed with me and that she had four partners before me and never used drugs. I'm sure you can see where this is going.

I found out that her and her previous boyfriend were poly and into a lot of crazy stuff, threesomes with both genders, using drugs, and obviously her partner count of both men and women was a lot higher than she said. Again, I have no problem with this lifestyle it's just not something I would want for myself or for the woman I marry.

I confronted her about this and eventually got the truth confirmed after a lot of evasiveness. She says all that poly/drug stuff before was what made her realize that she wanted the conventional monogamous marriage with loads of kids etc and a clean life just like me and only lied to me because she knew a man looking for that wouldn't want to marry a woman with her past. 

That makes sense because i'm seriously thinking about breaking up with her over this, firstly because she lied to me for so long about stuff she knew was important to me, second because of insecurity. Like she's the best sex of my life but what if I rank only 20th or something for her? Could someone who lived that life be happy with the "square" life with me? And since she's apparently bisexual could she ever be happy without women? What if she's only using me as the "safe" man she settles down with and cheats on me? If I marry her will I end up regretting that I missed a huge red flag?

Those are questions for me to decide on, my question to all you is: WIBTA to throw away the best relationship of my life over this? Or is it fair for this to be a dealbreaker and i'm about to dodge a bullet?