Tell me how can I not say that everything is a lie?

Tell me how can I not think that everything is a lie? when from the very start, I have already been cheated on and was made to believe I have found a God’s gift for me when truly it was a monster I have found. I didn’t know that during the time when we were already talking and he was already trying to woo me and build a relationship with me, he was still on a complicated relationship with his ex and they were still seeing each other? And just a few days after we became officially together, he still slept on the same bed with her? While I was enjoying the bliss of finding someone who I thought was real to me and someone who I thought will be my home, I didn’t know that it was a person who can lie to me at the very start was the one I found.