Good ol' breathing

Hi All, I have a problem with my breathing. But before I go into details here's a little background of me. I'm a 39 old 6'1" 83 kilo (183lb) in-shape (?) male. In my younger years I was kickboxing, kayaking, rowing, soccer. I like sports and am not a couch potato, doesn't look like one either. Have broad shoulders, long arms. Not bulky, but fit I would say. I do like sports in general but with breathing I always had troubles. Despite of what would someone think when looking at me I was always almost last to finish the long distance run in school or anytime I had to do something that required me doing something for a long period of time. With swimming I experience the same. My average swimming session looks like this: 1 hour lap swimming covering app. 2000 meters. Free-back-free-back-***-back in a 33 meter pool 1:30- 2:00 break. Sometimes I do mini-IMs, so even butterfly is not out of question. During practice I push myself as hard as I can. Swimming against the clock. Trying to be faster and faster every time. Cutting back on breaks and trying to be faster when swimming. I am completely out of breath after each set. Since I am a technical guy, I have read tons of articles, watched hundreds of tutorial videos. I know all (well, a whole lot) about body, head positions, catch and pull, rotation, high-elbow, being relaxed, breathing patterns, kicking cycle, etc. and as much I can tell I built those in in my swimming. When swimming I try to look myself from the outside and imagine my body and compare it to what I have seen from elite swimmers. In my early years I attended swimming schools where and even a few years ago I had a swimming coach. I was told to have a good style. I swim with high elbow in and out of the water, rotate my body when rested. The problem starts after 2 laps... So when I start I glide through the water, calm and relaxed. Have no urgency to come up for air at all. I do come up after every 5-7 strokes however, but I could make that 9-11 too. It feels like I could go on like this forever. But that's just the first lap. After I reach the wall I turn to my back and start backstroking. My breathing starts to get faster. Buy the time I reach the wall again I breath at every stroke. And the 3rd lap (free again) is very different from my firs one. I am tired like hell, have to come up for air every 2 strokes, my arms are heavy (there's vomit on his sweater already, mom's spaghetti), breathing is not controlled (hyperventillating I believe), heart's pumping fast, have to fight to reach the wall. I somehow manege to finish my set and take at least 1:30 minute break to catch my breath and be ready for the next one. And it starts again. The first one is very easy, but the same thing happens what I wrote above. I think that I hyperventilating and even though I try to exhale all the O2 I do something wrong and the CO2 builds up. That is why my lung can't keep up and I have to come up for air. If you guys have any tip (technical, medical) on what causes how to prevent this, please let me know. I do think about having a coach for a longer period of time and let them correct me. Thank you in advance