OMG - fat, bloated, and lonely! Just cracked me up. I've been there!
Listen, don't call yourself names because you keep comparing yourself to others - we all do that from time to time. It's pretty much an automatic thing we're taught to do because humans are competitive creatures. Sometimes, it's a very useful thing, as in strategizing on how to stand out in order to ace a job interview, for example. Don't be so hard on yourself that you are hard on yourself for being hard on yourself!
The only thing we can do to manage certain patterns in our thought processes is to be aware of them without judging ourselves for having that habit or pattern, and then pay it no mind. As in, "Oh, here I go again comparing myself to her. I don't have to do that." And then you just occupy your mind with other, more productive things to think about, like, "Maybe I'll rearrange the canned goods in my pantry now," and really get present with what you are doing rather than indulging in thoughts. Eventually, the thoughts become background music that you know is there but don't have to pay attention to.
But, in addition to all that, discuss with your hubs all the fears you mentioned here. "Honey, even though we were both happy that neither of us wanted to leave if you got involved with someone else, I now have this creeping fear that once you find what you're looking for sexually, you won't need me anymore for anything. I'm comfortable with you having sex with someone else. You loving someone else scares me, and I keep comparing myself." As long as you aren't giving ultimatums or making rules out of these fears (as in a very unreasonable "don't fall in love"), just talking about them will help them dissipate.