Every time i get stunned my boxer seems to let every punch through and im really really slow so that i cant dodge or move away or clinch.  So its like if i get stunned its inevitable that im going to hit the floor.  
If i stun my opponent however they seem to be just as fast as they were and they block every single punch 100% of the time. 
 
Am i doing it wrong?

i had a similar problem, and when i tried to block he moved his head forward and down as if he wanted the next uppercut to hit him just perfect.

To survive being stunned.....You'll want to keep away from them altogether. Use the push button to get some distance and then move away, but make sure you aren't holding block as you move as that slows you down.
 
To knock them down.....If you are starting out in Legacy mode then you're going to find it hard to get through your opponents defence when you have them stunned as it's only really quick  combination punching that are going to get through their defence. I had very few knock-downs for the first 15-20 fights.

this game is pretty fucked up.... summary of my comment (whine whine whine so read on if you want)
 
I've played 2 games online.  Destroyed the first dood.  2nd fight the guy immediately spams the same right hook over and over.  I think to myself...wow this is gonna be easy.  I counter him, counter him, counter him...etc. etc.  He lands maybe 1 for every 10 of those hooks and yet I get knocked down 3 times in the fight and only knock him down once when I'm completely dominating him.  I got knocked out.  Really don't get it...both our fighters had the same rating (given I dunno who any of these guys are). 
 
Stats were 50% of my punches landed to his 35% to the head and body was 51% for him and 46% for me.  So I landed more punches.  I landed 37 counters on him....37 to his 9.....and I am the one that got knocked out?  He threw 455 POWER PUNCHES and landed 162 of them.  I threw 101 power punches and landed 43 of them.  So he basically spammed the same power punch over and over missing waaay more than connecting.  Why was he not completely gassed? 
 
I really don't get it.  I hate this game already!  Sorry I just needed to rant somewhere and didn't think it needed a new thread. 
 
well...other than that, the game is fun ;/ 
 
edit:  Alright, now I've played about 7 matches online.  I'm 1 win and 6 losses.  Compared to my Round 4 record of 100+ wins and 4 losses.  Mmmmm, apparently I just completely don't get this game.  I land literally (i counted) 10x more counters and power shots and I lose still on the judges score cards and end up getting knocked out.  Game is getting sold for Yakuza 4 I guess.  /game ranting over

Game is really frustrating me at the moment. Playing on Champion difficulty in Legacy mode, so far my record is 17-4-2 9 KOs, but recently I've just been turning it off in frustration. I'll dominate whole fights, landing 400+ punches and getting their damage up to 80+, completely closing eyes and producing cuts. Yet I can't buy a knockout, while the AI will hit me with one body punch and I'll go down straight away. Just losing fights now because I get stunned off random punches, even when my stats for chin and heart are very high. Whereas I continually hit them with power counters etc, and they don't even get rocked.

There's something about the "balance" of this game that seems off. I bludgeon dudes in Legacy Mode with high % of landed punches, yet they stun me on one counter punch to the body. Even with the Heart, Chin and blocking ratings built up, I'm struggling to not get destroyed once I get inside (I'm set up as an "inside fighter").  
 
It's not a terrible game but it seems the balance isn't quite there during some fights.

Wow it sounds like all the stupid shit from Round 3 is in here.
 
Glad I decided Marvel vs Capcom 3 was good enough.

Having the same problem with the game, DESTROYING duders in fights but cant get a knockdown/knock out. Its stupid when they can nearly knock you out with one punch. Been playing this game all day, only got 2 knockdowns the whole time. No knockouts
 
Game is getting sold this week :( Sad because it had such promise but the balance is fucked

Sounds like the same shit from FNR4 where normal punches became worthless because they hyped up the counter punching so much.