It’s extremely intense to have a baby emotionally and physically. It’s totally normal not to feel like you have any more of you to give.
If you are breastfeeding it’s especially physical so the thought of more needs needed of you can be too much.
There is absolutely nothing wrong and beru normal to feel this way.
Some women feel totally opposite, it totally depends.
Don’t feel that you need to justify how you feel if you feel like this.
Good luck !