Jjemas I'm sorry to hear that.
Getting a good night's sleep is essential for your brain and body to function 100% the next day. I have had sleep problems all my life so will try to offer some insight into I have learned.
It could definitely be your mattress! Everyone has a different shape and back and requires softer or firmer mattresses. If you've always had trouble sleeping on this mattress then that might be it.
Make sure you are not exercising too late as your endorphins will keep you up late.
Try not to eat too late as this will cause your stomach and digestion to be active into the night keeping you up.
Make sure to not look at any screens 30 minutes - 1 hour before bed. The bright light does not allow your brain to shut off and can cause sleep problems. Or use the "night mode" function so it is yellowed out for you.
Reminder, I am not a doctor and if this is regular you should see one! However I hope this can help a little or add some insight. I know what's like to not sleep!