Swich background images stretching while customizing in android

I am trying to customize Switch. I used xml files to achieve that switch_bg_selector.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://ift.tt/nIICcg">
<item android:drawable="@drawable/cd_filled_toggle_round_bg" android:state_checked="true"/>
<item android:drawable="@drawable/cd_filled_toggle_round_bg" android:state_checked="false"/>
<item android:drawable="@drawable/cd_filled_toggle_round_bg"/>
</selector>

and track_bg_selector.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://ift.tt/nIICcg">
<item android:drawable="@drawable/cd_filled_toggle_bg" android:state_checked="true"/>
<item android:drawable="@drawable/cd_filled_toggle_white_bg" android:state_checked="false"/>
<item android:drawable="@drawable/cd_filled_toggle_white_bg"/>
</selector>

and the code for switch is

<Switch
android:id="@+id/toggle_email_diss_invi"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_centerVertical="true"
android:layout_marginRight="10dp"
android:textOff=""
android:textOn=""
android:thumb="@drawable/switch_bg_selector"
android:thumbTextPadding="25dp"
android:track="@drawable/track_bg_selector"
/>

the background image I used is sliced for all xxhdpi, xhdpi, hdpi and mdpi but the problem is that the images are getting stretched. I spent many hours to resolve this issue but didn't find appropriate solution. I am attaching the screenshot that how my switch is looking.

and how it should look like is