I think that it is very thoughtful of you to realize that you relied on him so much. I actually am in the same situation, but on the other side. My girlfriend and I were together for two years; within those two years, I always encouraged her to maintain friendships and relationships with family, but she never did. She relied on me for A LOT. It did not bother me one bit, but I think it must have been hard on her when I spent time away from her with family and friends. Because she had not maintained those relationships, she seemed somewhat resentful at times. Recently she has taken time away from me and in reading your posts, I have a strong idea that she must have some of the same feelings you do. I miss her like crazy, but you know what?? I'm more proud of her than anything. I am proud of you too- this is a very big challenge and I know you will succeed.
Do you have any hobbies? Sports can be a good way to meet people while still doing something for yourself. Tennis for one, is a very social sport and you could meet lots of people that way. I know some communities have walk/run groups... maybe you would be interested in that? Like someone else suggested, asking an acquaintance or neighbor out for coffee is casual enough to start without being overwhelming for either of you.
Reaching out and taking risks with new friendships can be scary, but if you know it is what you need, you will overcome that fear. My other advice to you is that if you truly care about your boyfriend, do the best that you can to explain the way you are feeling to him. I know that, also, can be tough. He will likely have questions and not clearly understand, but that is because he cares. Just like it will be hard for you to be away from him, its very hard for him too.
In the end, you will have more independence. I have learned from this forum that taking care of ourselves is of utmost importance in order for us to be able to take care of others when necessary. Remember though, being independent doesn't mean you have to take on the world alone. Now, instead of only having your boyfriend to rely on, you will have other friendships as well. We all need someone at one time or another... if you care about him, make it clear that this is about YOU and YOUR NEEDS.
One more thing... Because you are realizing changes that you want to make in yourself, it also means your relationship with your boyfriend will change. Although me and my girlfriend and not "together" right now, I do know that if/when that day comes again, our relationship will not go back to being the way it was, and that's a good thing. She will be more independent and able to offer more in the relationship, just like you will with your boyfriend. Changes are sometimes scary, but they are necessary for improvements in any part of life.
Being able to post in the forum has really helped me and I hope it is useful for you too. Good luck!