New Swimming Question

So I think things may be going pretty well for me in the pool.  I've been told by one of local coaches that my form is ok and we've got a couple things I've got to work on but it's fundamentally solid.  Glad to hear that it's still there after 20 years, lol.
Here's my question; I want to be able to do 100 yard sets and I'm having a hard time doing that.  Tonight I got in 1 100 yard set and 1 75 yard set.  If I give it 1-2 minutes between 50 yard sets I feel great going down and most of the way coming back.  My first thought is that I need to slow myself down but I don't know how!  
Looking for thoughts or 'don't worry it'll come'.  It is getting easier for me to do 500 yards (I know not a whole lot).  My goal is to swim 4-5 times a week.  12 weeks to my first Oly triathlon (first one ever) so I'm starting to wonder if I need to drop down to a sprint.  Am I wrong thinking that once I get a good stride going adding the distance won't be that hard?
Thanks!
--Dan 

Hey Dan,

     A couple thoughts on your post. How's your breathing? How many strokes do you take between each breath? (Should be 2 -3) Also, maybe you are kicking too much and too hard! Your quads are the biggest muscle group in the body and require a lot of oxygen when fully engaged. Tri swimming is much different than speed swimming in that you want to try to  use your legs as little as possible in the swim and conserve them for the bike and run. You should try using a Pull Bouy once in a while (The ones you hold between your thighs) it keeps your hips and lower body boyant and allows you to work on your stroke and breathing without worrying about your kicks. Don't become relyant on the bouy though... it is just for technique building. Also you could try some hypoxic breathing excercises after you get a more confortable breathing pattern down. For example: If you alternate breathing every 3 strokes.... Warm up with a set of 200m normally, follow that with 3 x 50m breathing every 5 strokes, then 3 x 50 every 7 strokes, etc... it really helps increase the lung capacity and actually helps out a TON with your running as well ! Some food for thought, butas you stated, it will get better. My guess is that you are kicking too hard and are having a very high turnover rate on your strokes. Focus on LOOOOONG smooth, gliding strokes, rather than fast , repetitious slaps in the water. Do some strength training on your triceps... This is where your power will come from on your swim! Take care and don't you dare go to a sprint distance!!! Push yourself big daddy, you got this....