Nested Scrollview can't scroll until the bottom (constrained) - flutter

Question

I'm new to flutter development and I'm trying to create a contact book page that will load recent contact and all of my contact list, I managed to get the data and build it into the widget.
The problem is when there are a lot of contact (let say 20 contacts). If the screen size is small it can only scroll until 7-8 contacts, but I know there's more to it. But I guess my nestedScrollView won't let me to scroll down anymore.. Like it's constrained by something
what's the problem and how to fix this ? Here's my code:
/// BODY
body: WillPopScope(
onWillPop: () {
print('hello');
},
child: ListView(
physics: BouncingScrollPhysics(),
shrinkWrap: true,
children: [
Container(
padding: EdgeInsets.symmetric(horizontal: 20),
height: MediaQuery.of(context).size.height,
child: NestedScrollView(
controller: _scrollController,
headerSliverBuilder: (context, isScrolled) {
return [
SliverPersistentHeader(
pinned: true,
floating: false,
delegate: ChooseUsersHeaderDelegate(
widgetList: Container(
color: Colors.white,
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
/// Build Search Box Function
buildSearch(),
],
),
),
minHeight: selectedContactId.isNotEmpty ? 135 : 60,
maxHeight: selectedContactId.isNotEmpty ? 135 : 60,
parentContext: context,
),
),
];
},
body: Container(
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
/// Recent Contacts Subtitle
Text(
'recent',
style: GoogleFonts.montserrat(
fontSize: 14,
fontWeight: FontWeight.w500,
color: primaryColor,
fontStyle: FontStyle.normal,
),
).tr(),
/// Recent Contacts
Column(
mainAxisAlignment: MainAxisAlignment.start,
children: [
isLoading
? ReusableLoadingContact()
: NotificationListener<
OverscrollIndicatorNotification>(
onNotification: (overScroll) {
overScroll.disallowIndicator();
return true;
},
child: buildWidget(context, 'recent')),
],
),
SizedBox(height: 15),
/// All Contacts Subtitle
Text(
'allContacts',
style: GoogleFonts.montserrat(
fontSize: 14,
fontWeight: FontWeight.w500,
color: primaryColor,
fontStyle: FontStyle.normal,
),
).tr(),
/// All Contacts
Column(
mainAxisAlignment: MainAxisAlignment.start,
children: [
isLoading
? ReusableLoadingContact()
: NotificationListener<
OverscrollIndicatorNotification>(
onNotification: (overScroll) {
overScroll.disallowIndicator();
return true;
},
child: buildWidget(context, 'contacts')),
],
),
],
),
),
),
)
],
),
),