It feels like you've faked yourself into a corner! If you tell your boyfriend that you've been faking it all along, he won't trust you in the future. If you start being honest now and stop pretending that you are achieving orgasms, he's going to be confused as to why what he thought was working is no longer working.
The first thing that you need to do is to learn how to masturbate yourself to orgasm. Lonnie Barbach's book, For Yourself, will show you how to pleasure yourself to orgasm.
Once you know how your body works, you are in a good position to 'teach' your boyfriend what you like. You don't need to say that you faked it in the past. You can simply tell him that you want to want to deepen your sexual communication and expand your level of intimacy by exploring new and different ways of pleasuring each other.
As you show him these 'new' things, he will be so caught up in learning about your body and discovering other ways of delighting you that I think you will be able to move past your initial mistake. Let me know how you make out.