My iPhone is getting buggy. Again. But now, worse.

Question

I had my iPhone 4s for 2-3months now, and I just noticed that it's getting slower and buggier everytime I resolve my issue.
iPhone 4s
iOs 6.1.3
Free space; 7.1 Gb.
Experiences:
FIRST EXPERIENCE:
my iPhone was just a bit unresponsive at times. Lags sometimes. I was told to reset my iPhone by holding the home button and sleep/wake button till my phone turns off then turns on with the apple logo.
It fixed my problem. But this time it got worse.
NOW:
My iPhone became MORE laggy.
- When texting people;
1.) Keypad sometimes lags.
2.) The keypad doesn't show up and I can't bring it up whatsoever. Resolved this by closing the Messages app but it happens periodically which kinda bugs me especially when I need to send that important text.
3.) The sending rate of the message got slower. My signal bar is full, and the message is just about 30-50 characters.
- Using internet-related Apps (I surf the net in the room where the router can be found. And when using my laptop, webpages load instantly. So I could say that it's not network lag.)
1.) it loads kinda slow. And when it's loading, I can't move the page nor touch any button. Safari seems to hang so I press the home button which takes 3 seconds to respond. Or even not respond at all. But it all ends when the page has been loaded.
2.) When using the Facebook app, sometimes when I browse pictures or just pages, it hangs and closes the app. I don't experience this in the iPad nor my parent's iPhone 5's.
3.) in other apps it just hangs up and closes the app.
Misc;
When playing music, the whole bar where the signal strength is, what time it is, etc, gets covered by the music player. It happens rarely.
Well that's everything. Hope somebody knows how to prevent this from getting worse. :)
No negative emotions intended.
Apple Fan as always! :)

Answer 1

You have Reset the iPhone, now it is time to Restore it from your backup and if that doesn't work Restore it as a new iPhone.
http://support.apple.com/kb/ht1414