It’s great you are taking the time to reach out for some guidance and support with your situation. It sounds like you are feeling real confused and stressed out about what to do; and that is understandable seeing as how you feel like you’ve got to go behind your mother’s back in order to see and be with your boyfriend. It is great you have found someone who treats you so nice and makes you feel happy; having your mom be so disapproving of the relationship probably creates a lot of anxiety for you.
A lot of parents have a difficult time feeling comfortable with their kids dating and hanging out with members of the opposite sex. A lot of parents are afraid their kids will make poor choices, get STDs, have sex, or get pregnant; all of these are definitely things which parents worry about. However, all of these can be avoiding by making mature, responsible decisions.
It might help to sit down with your mother and talk to her about how you can prove to her you are capable to make mature and responsible decisions on a regular basis. Then, go out and do it. Here is a link which could help you have this conversation with your mother: http://www.yourlifeyourvoice.org/DiscoverIt/Articles/Pages/Howto.aspx.
Obviously hiding your relationship is just putting a lot of stress on you, so it could help to open up to her about it. Introduce her to your boyfriend; she might not be so concerned about you hanging out with a guy if she actually gets to know and meet him. This initial meeting could be a little awkward and tense, so prepare your boyfriend for what to expect.
Hang in there. We know it feels like you have a ton of stress on your shoulders, and the only way to deal with this stress is to deal with the situation causing it. Obviously this is much easier said than done, so take some time to gather your thoughts and figure out what you want to say to your mom. It helps to avoid getting worked up, yelling, or arguing/blaming your mom. To answer your question: the only way to continue to see your boyfriend without lying to your mom is to actually tell her about the relationship.
Hang in there. It is normal to feel confused or stressed out by this type of situation, so hopefully our response has given you some steps to consider as you try to work through this situation with your mother. We are always here for you, so keep in touch. Let us know how things go or if there is anything else we can do to help you.