My Current Situation

Hello, I currently found out after catching my boyfriend looking at things online that he is interested in pregnancy. but it goes farther then that. he says he often visualizes how it would be if he himself were pregnant and it excites him. he looks on deviant art at butt expansion or breast expansion stories and looks at videos too and gets off to them. I knew before that he was sexually attracted to pregnant women but I never knew he felt this intensely about it. since I'm very uneducated on the topic I don't want to jump to conclusions about his psychological health or judge him in anyways. I love him so much and would do anything for him. the last thing I want to do is leave him because he has a certain sexual preference that may be considered taboo. he says he's not homosexual and isn't turned on by guys having sex. he says he doesn't necessarily want to be a woman but is just interested in the growth process of pregnancy and wants to experience it himself. if anyone has any advice or has also experienced this in a relationship let me know. I just want to understand. thanks.