From your previous posts it looks like you do have a sexual relationship with your boyfriend, as the two of you are engaging in some sexual behavior. A you referring to a specific kind of sex?
A relationship -- of any kind -- is with a person, someone we know. It's not abstract, it's specific. And you probably don't want to be in this kind of relationship with just anyone.
So, the best place to start is usually with who, specifically, you have these kinds of feelings for and would want to pursue this kind of relationship with. Is there someone you have in mind?
Never doubt that a small group of thoughtful, committed citizens can change the world. Indeed, it is the only thing that ever has. - Margaret Mead
We can't really pick a person for you to decide you want to pursue a relationship with. That sort of feeling arises organically from getting to know other people. Something we can help with is brainstorming ways for you to meet new people (since it doesn't sound like there's anyone you're interested in right now) who could be potential partners. Does that sound helpful?