I suffered greatly with the pool-flu (posted another thread somewhere) and someone suggested nose-clips, so I've tried those and whilst it takes a while to get used to the feeling and over the embarrassment of the wonderful sartorial statement they make, I have found that they really do make a tremendous difference.
I was exactly the same when first starting to try front crawl ... took lessons and even then couldn't do more than a length without my heart and lungs making a bid for freedom.
Eventually I managed two lengths of front crawl, so for my first half last year I practised with 2 lengths FC then 4 of breaststroke to recover, repeat until finished.
After the half (of which I actually breaststroked about 90% of !) I didn't swim for a few weeks, got back in the pool and was back to square one ... 25m and die ... which was ridiculous I could run for 7 hours on an Ultra yet 25m in the pool and I was finished.
Kept at it, solely trying to work out how the hell I could breathe, managed after a few weeks to get up to 4 lengths continual FC but that was a struggle, then it clicked ... don't know what .. don't know how .. but it did ... doing my usual 4 FC, then revert to breaststroke for 4 to recover then back to FC, all of a sudden I found I didn't need to go in to breaststroke to stop the impending cardiac arrest, and that day I just carried on swimming and did a mile non stop with 90% of it FC ... (I was like a T-Rex after, as my arms were completely fecked!) ... it was absolutely bizarre .. and to this day I don't know what happened or how, but it did .. it just 'clicked'.
I'm still slower and less graceful than a wind up turtle bath toy but I've finally mastered the breathing. So I think what I'm trying to say in all the above waffle is .. keep at it .. it WILL click for you too !!