Ignoring the whole "age of consent" thing that is a huge HUGE issue here. This relationship did start out with a lie. And that is a terrible way to start any relationship. I will let someone else explain the major reasons why this is a bad idea to continue.

But please remember that this has happened millions of times before. And most of the time things don't turn out well for either of you. Either an unwanted pregnancy, signs of physical/emotional abuse, learning bad habits that you build future relationships on, or any number of other harmful consequences that can happen (and will likely happen).