plan b? PLEASE HELP

So lately I've been having this "hook up" thing i guess with this guy I've been talking to. He usually takes me do something fun during the day and then when we get done he takes me to his house and it always results in sex.. sex with him is so good I literally cry everytime. We only did this three times.. I don't know how he feels about me because his stance on me changes so quickly. Like one day he'll be snapping me and talking and flirting and some days he doesn't even think about me. Anyways I'm not sure if we'll ever hook up or even hang out again but i want to get plan b just to carry with me incase he wants to meet up again. Everytime we had sex he always said he wanted to cum in me and tbst he was always so close to doing it. I really want to experience it also. And he seems like he really wants to. I have serious feelings about him even though he doesn't feel shit about me so I want to make him happy and maybe do this. On the other hand I want to let him cum in me and not take plan b because i desperately like this man and i wouldn't tell him i got pregnant because he'd be mad and hate me but i kind of want something that'll keep us connected for the rest of our life. I wouldn't tell him until I've had our baby. Is this crazy? Anyways please give me your opinion on plan b! Is it worth it just for him to come in me?