It depends (oops - no pun intended) on what dynamic you both have in the relationship. It may be that he wishes to please you and participate in your fetish. I note that you just enjoy wearing and don't consider yourself an ab or dl to any degree. If it is the thought that he may have control over you in some way, this seems a little odd on your behalf. In my experience, ab/dl/fetishistic activities tend to entail a some degree of submissive/dominant behaviour if two persons (who know the other is wearing) are involved. It may be that he is coming round to possibly exhibiting care-giver behaviour.
From your previous posts / info supplied, it appears he has accepted this side of you. My advice therefore is to be thankful he hasn't rejected your love of wearing nappies, and is showing some interest. In a married couple situation, this cannot be a solitary pursuit and if it is, can lead to friction, feelings of guilt and concealment if one partner just "doesn't get it".
Perhaps you might ask him outright why he wishes to buy for you. This doesn't have to be forceful or defensive. It can just be an innocent, jokey aside. I wouldn't however let on at this stage that it has made you a little apprehensive/uncomfortable. Just go with the flow and don't feel worried about it.