How can a Christian go from being a Christian to a muslim?

This weird story freaked me out. It's kinda long so listen. Back in high school there was this boy I talked to, he had a gf previously before me I knew of her we all went to school together. He ended up breaking up with her because they couldn't get alone because he said she had become annoying. The girl was still in love with him. One day at school she approached him while I was sitting besides him and questioned him was where he had become at the point after their breakup and who he chosen decide to be with (me) was really what he wanted. Time flew on, I got over it him it's apart of my past I don't really acknowledge because I feel I came so far from where I came . I feel I was a bit in the dark and not knowing fully then so much about the importance of the choices you make in life. Over time I feel like I have grown to become a better person and I feel that god has been besides me , and I feel like ive been blessed. An old friend I knew of drooped into my life we fell in love and been together for a year and it's been going on nearly 2 years since we've been talking in total during being together and apart now. But I was just thinking about the past and having flashbacks. and thinking was I wrong for being in that predicament when that boy made a decision to be with me after breaking up with his ex ( I remember seeing them together ) hence we all went to school together and from a distant it look like they both may have been in love . And to see her in that hurtful situation seeing that her ex boyfriend who she loved was with another girl. and I feel was it rude for me to take that position knowing that those two had history together ? and I just find out the girl recently became a muslim not that it's important.. what are your thoughts? Do you think I was wrong?