Will he ever leave that habit?

well ive been dating my boyfriend for a while now and we are engaged, but before that, he was a loner in high school and stuff because he was fat and got made fun off. He got tired of it and lost the weight, but he also had yahoo answers and posted and answered questions with lies. one of the main ones i was concerned about was about him having a little girl and twins on the way (this was before we started dating) we argued about it once about a year ago and he said he wouldn't do it again. but i still found some recent answers and questions from him that were still like if he was a different person. i made him delete his yahoo account, but should i be concerned?