Playing against computer

I normally play against Computer (medium strength) and lose always.This is one of those games.I play white.Any suggestions?

I have plauyed a lot against Computer (Easy Strength).

I usually make a lots of mistakes it seems.Pointing to a specific one and how can I turn this game into a winning one for me will help tremendously.

 Thanks Richard for your advice.

I feel i might be a bit too new to kibbitz, but just a thought here:  it seems like the computer will always choose an exchange over a retreat.  At 6...Bg4, you respond h3.  The computer is definitely going to take your knight at this point rather than back out of Bg4.  Your only recourse is to weaken the castle with 8 gxf3.  What if you had gone Qxf3 instead?  Too early to move your queen out?  I don't know... But I think the point at which your castle was weakened marked the decline of your game.  If you had not responded to 6...Bg4 and move your queen from the pin...maybe it would have changed the outcome?  Arguably something like Qe1 in response to 6...Bg4 could have still resulted in 7...Bxf3 where you really had no choice but to respond by doubling your pawns and weakening the castle.  But then again, had you not done 7...h3, it may have given you more time-- black may have chosen to wait a little at its own expense before take f3.  By the way at 12.Bxh5 I wasn't really sure of the reasoning.  I understand the threat on b4, but then after 12, Bxh5, black has two possibilities for the h-rank for its rook.  Anyhow, I usually lose too.  Thanks for sharing your game and giving me the opportunity to give you my thoughts.

Thanks Richard and tom for your insightful suggestions.I won the first time today against Computer -Medium which I guess , has to do something with your posts.