Health insurance question

Does anyone know: if you don’t have health insurance, but your boyfriend ( living together) has one ( true military job) and you are not married and you get pregnant, can you be part of his health insurance plan? I was reading that some insurance as soon you lived 6 months together and share most of the things, you are considered domestic partnerships. My concern is: I don’t want to get marry soon, not now, but I want to get pregnant lol 😂. So in case I get pregnant, I want my man to put me in his insurance for our future child. I feel I running more of time to have kids that getting married.