One way to think about things is that you really ARE in a tough situation, and anyone would have trouble dealing with the loss of intimacy. It would be hard for anyone in this situation to be 100% happy all the time.
So, given that you are in a tough spot, the best thing to do is to be kind to yourself. Instead of beating yourself up for sometimes hating your life, remind yourself that anyone would have a hard time dealing with being the main breadwinner, new mom, and having a dry spell in her marriage.
Once you've given yourself "permission" to have mixed feelings about your life, then it will be easier to also remember the good parts of it. Many men would take their family's side against their wife, but yours has stood by you through thick and thin. Yes, it's hard having a young baby, but yours is calm and doesn't cry. Every wife and mother has days they wish they were still single and carefree--it's just human nature. But if you really were single, you'd have to be out in the dating world again--and that's not a very nice place to be these days. Women are getting their hearts broken by "players" --and you never have to go through that ever again, if you don't want to.
So basically, don't expect yourself not to have any negative feelings about your situation. There really ARE two sides to this... a good side and bad side. And that's okay, as long as you remember that BOTH sides exist, and don't just dwell on the bad.