We all have different sex drives and they can fluctuate wildly over the years. The key thing is to be able to talk about it and work through the highs and the lows - together.
And yes, there are definitely women out there who like to have sex - a lot!
Stop trying to put blame on either or you. It doesn't have to be anyone's fault. It just is... When we get into the 'blame game', things can go down hill very quickly, whether or not you express these feelings of blame to your partner.
Also, I know it's a challenge not to keep score - I used to be really bad at it and am still working on that issue. But if you can just accept things as they are, right now, today, and apply what you've learned to your next relationship, it'll go more smoothly.
As far as her being insensitive to your weight loss goals, all you can do is communicate how that makes you feel. Yeah, this is a tough one for men, but you have to keep it about your feelings and not attack her for not doing what you ask. you cannot control another persons actions, emotions, or feelings. You'll just get frustrated trying!