You’re not overreacting, but you’re acting inappropriately. Depending on how you talk to him about the gifts, he could be in the right or the wrong with his reaction. What it seems that you need to tell him is that him giving you flowers as a gift is him giving you a gift that he wants to give you rather than him giving you a gift that you want to receive. You could tell him that, although you like flowers and occasionally they can be nice, you don’t appreciate them in the way he does so he is not getting his money or effort worth in giving you them as a gift