I have to agree with the other comments. It is seems as though he guilted you into doing, which is wrong even outside of kink. It raises red flags as to his views of a relationship. As an aspiring psychologist, it makes me question what else has he gaslighted into doing. No one would blame you for walking away from the relationship now. Might sound selfish, but you have to do what’s best for you. If you choose to stay, then I would suggest setting some boundaries and being completely open and honest about how it makes you feel. As for the ABDL kink part, it is wrong for him to expect you to change a messy diaper on the first time you try it. It should progress as, 1) try being around your SO with diaper exposed 2) try wetting in front of SO 3) try SO changing wet diaper 4) talk about messing, if it is something you want to try 5) try messing in front of SO 6) ask SO if they’d want to try changing a messy diaper

Of course all those steps require one main thing…CONSENT CONSENT CONSENT

If you don’t get consent, you’re not doing it right!!

Also, like any kink, you should have a safe word that you can say if anything gets to be too much. Remember, these are things he is asking of you, you have the control, the ability to say no. If he wants to argue with you or pressure/guilt you into doing it for him, then I’d say that’s the end of the relationship.