@ashley2819,
ashley2819 wrote:
I'm being acting like a needy little child for feeling like this.
That's nonsensical. Those are legitimate feelings.
As for the other things? We really wouldn't know. Was he always reserved or this a relatively recent mood change? Hopefully he's not feeling guilty for doing some untoward things with others outside of your current relationship.
The only person who would know this answer is your partner. Unless you hire ... say... a private investigator to see if he's having an affair or something. Ask him. Maybe he's just depressed and needs counseling.