It always annoys the shit out of me when guys think being a "nice guy" won't get them anywhere and every girl wants an asshole. False. If you're looking for an insecure clingy girl with daddy issues, sure, be an asshole. If you're looking for a legitimate relationship, it's a little deeper than that... and it has just as much to do with the girl you're with.
I was in a relationship with a "nice guy" that lasted a month, and I was with a huge asshole for 6 years. It has nothing to do with that, but I will say that being with the asshole fucked up my self-esteem and manipulated me into thinking he was all I deserved... I felt stuck with him for our entire relationship, thinking the alternative was to be alone for the rest of my life. He didn't cheat on me that I know of, but he tried at least once and lied to me over and over. He was always quick to accuse me of doing things behind his back and that's when I knew he was doing something he didn't want me to know about.
You can't just jump into relationships and think that just because things are serious now means you've found your future wife, especially if things are just "okay". The most important thing to look for in that person is their personal values and priorities in life - they need to match yours. You said it yourself that something didn't feel right throughout the whole relationship. Lying is a big deal, even if it's about the stupidest shit... you never know what they're REALLY lying about, it's all a suspicion.
So, to answer your question, yes, you are doing something wrong. You're trying to look past issues like any decent guy should... but it sounds like you moved too quickly into the relationship to really know who she was as a person. You'll know when you find the right person, just keep trying, I'm in the exact same boat.