Boyfriend wants porn star sized implants, but I think maybe going from a b cup to a d cup sized?

A fantasy. The boyfriend has a fantasy of female beauty and desirabiity based upon his looks at porn where large breasts are at a premium. If your personal desire is to increase your cup size, by all means consider it. If having breasts the size your boyfriend fantasizes about, and that is the basis of the relationship, you might rethink things. Your size should be self pleasing; boyfriends are transient.
You decide. It's your body! you decide what you want. Just be aware that large implants may lead to back pain. And will you be happy with whatever size you choose? Friends, family, work? Talk to your friends and your surgeon. Ultimately, it's your decision. You have to live with it and you're taking all the risk - no one else.