Out of Breath and Slow, advice?

Need to start with a little background info before my question... I started swimming laps for the first time last July. I have had a lot of lessons, stroke clinics, I took an advanced TI based class, I've been video taped with coaching afterwards. I think my technique is pretty good (not great, but decent for a relatively new swimmer). I was swimming 1 hour 3 times per week, recently I cut that back to 2 times per week due to shoulder problems. I also kickbox, step aerobics, mountain bike, lift weights, yoga. I can do high intensity land-based aerobic activity for 1 hour with no problem. I workout 1-2 hours a day 4-5 days per week. I have lost 62 lbs., still have 35 to go. Weight is coming off nicely, about 1 lb. per week. I recently had a fitness test and I came back good on flexibility and cardio, and excellent on 2 different strength tests. Now that you have my background and fitness info here is my problem. First, I run out of breath swimming. I can keep going but the first 10 laps or so I feel like I'm suffocating. I noticed it a lot in a recent stroke clinic. Everyone there said my technique was the best in the class, yet after just 25 yds. I was breathing heavy and they were not. Second problem is I'm really slow which I'm starting to think is related to the first problem. It's hard to go faster when you feel like you have run out of air. My lap time is about 53 seconds best time, more like 1:10 on average. Terrible I know. I talked to a friend recently who does a lot of different exercises and she said you know maybe you are just a slow swimmer. Some people aren't "built" to swim fast just like some people aren't "built" to run fast. Do you think this is right? Is my problem bad breathing technique? I've had the coach look at it and she seems to think I'm doing fine. Am I rushing it? It's been almost a year since I started swimming. Is it the 35 remaining lbs. holding me back in the water? If so why doesn't it hold me back on land aerobics? Any tips, ideas, suggestions are welcome. I don't compete so it's not about having a "winning" speed, but I'd like to be able to swim further in the same amount of time. Call it a personal goal. I'd also like to be able to swim without feeling out of air all the time. Thanks!