I know how you feel, but please don't worry. HPV is such a common STD that 80% of sexually active people have it. Most of them don't have any idea though, because most people never show symptoms of the virus. They can pass it on, but have no symptoms. Don't be so hard on yourself....its a lot more common than you think.
As far as telling your boyfriend, just be honest, straight forward, and get it out. Make sure to tell him the facts though. Let him know how common it is, that most people who have it will never show symptoms and that if you do get warts your immune system usually fights the virus and you usually won't have breakouts again. Let him know also that the virus can lay dormant in someone and then show up years later, so this doesn't necessarily mean that you cheated or he cheated. It also doesn't mean that you necessarily gave it to him. He could have been carrying the virus and passed on to you, or it could have been the other way around. There is no blame to be placed, since its such a messed up and confusing virus. You will never know who gave it to who or when you got it.
The more you learn about HPV the more you won't feel as disgusted or disappointed. The doctor should be able to prescribe you something to get rid of the warts faster. My doctor prescribed Aldara and it took about 6 months for the warts to disappear. I haven't seen any since. This is just a very annoying bump in the road and you will get through it. You can't turn back time, so the best thing that you can do it take care of yourself and move forward. It'll be fine.