I don't want to give back the things I gifted my ex because she gave them back after the breakup but changed her mind
I am not sure I understand the basis of your thinking here. Why wouldn't you give back the gifts that were for her?
She loved it and were super happy with it. Why would I give it back then. I don't know why she changed her mind about the gifts.
You should not keep things that don't belong to you. If these items were gifted to your ex, then you have an obligation to return them to her or you could suffer from a lack of character and morals.
I'm now in control and may want to use them.
When people give a gift they do not expect to later be able to keep it. This would be very rude of you to do this to her because she may need those things.