4S not notifying me about messages?

Not sure if this is an problem that has occured with anyone else, but there are times when I receive a text and my phone will be on loud, but remain silent when i get a text. This would result in me unlocking my phone, and being shocked that my phone would be on chest and not even notify me. I know for sure that it's not me just not hearing it because its happened more than once.

Additionally, I've witnessed a few times where my phone would be locked and receive a text and my text tone and screen would light up for a split second then turn back off. Then when I hit my home button to unlock.. it would finish the tone laggy and my keytone for my password would be laggy as well.

I've tried hard resets and everything

Thanks
Ace