iphone notifications wont work on locked screen but will when opened

So my iphone wont make a sound OR vibrate when someone texts me.

If i have it locked and laying on the bed and someone texts me, my phone wont tell me. I have to manually open it to see text message notifications. However if my phone is unlocked and im scrolling on facebook or doing something and someone texts me, I get the sound OR the vibration (depending on if i have it on vibrate).

I hear email chimes when the phone is locked but its just my text messages

The phone is NOT on do not disturb.

I turned the volume all the way up then all the way down and back again.

i turned on airplane mode.

i turned my phone off and back on.

I've turned vibrations off then back on.

Checked the ''message'' section in my phone and everything is fine.

I had this also happen like 2 weeks ago and it fixed itself (or i did something)

any ideas?