Stop trying for a baby ASAP and break up. If you do get pregnant and settle down, the issues with his sexuality will likely not resolve themselves. You don’t deserve to be “cheated” on even if you decide to technically allow it, and you also don’t deserve to have a partner that resents you for not letting him explore other options. You’re both young. He needs to figure out what he wants for himself, and you deserve someone that is certain about you.