I feel that I'm the least qualified person to comment on this..... Yet I seem to be constantly fighting through all sorts of problems myself. So here goes.

1) If you only breathe to one side I can see how this could happen. You are just favoring one side. I'm not sure if this is the case. Cure is bilateral breathing. As that will even everything out.

2) I find that my hip will fatigue if I'm "reaching" with my legs. Meaning I'm trying to lengthen too much and I'm not in a relaxed kick. I find I do this as I fatigue because I start pulling my head up further out of the water to breathe and so my legs drop....and my legs try to push a bit harder to make this happen. So it's a matter of getting your breathing technique back where it's supposed to be.

3) You are way beyond my skill and were hoping for a much better answer than this :-)

Good Luck