Hi Greg,
Sorry to hear she's having difficulty...but I think it's pretty normal...we go from one extreme to another and if we can't focus on the positive it seems like we trade one ego affecting problem for another...first we're too fat and then we're too flabby...it's about self esteem...
I wonder, is there a support group around she can attend? It might help if she can talk to others who've gone through the same thing..or even a regular counsler..maybe even an anti-depressant..
As for the air, it happens and yes it's embarrassing, I think because women aren't supposed to make noises
...I found it seemed to happen if I wasn't "stirred up" enough, same with the discomfort...to be blunt, is she lubricated enough..you could always try using a good lubricant.
Our (women) libido's are so tied up in the way we see ourselves and we are VERY critical of ourselves, more so than others are of us. One thing to keep in mind is communication is imperative...
You sound like a really sweet and caring husband...she's fortunate to have someone who's concerned with her well-being...
Hope this helps...
D