Have you really let yourself go, or, as you imply in your message, have you simply stopped dressing "sexily" (because the aim of that particular attire was fulfilled!), and now are simply groomed and presentable? Our culture currently privileges (very young) women who dress provocatively, and falling short of that can seem to mean "letting yourself go". But you may still be dressing neatly and nicely enough.
Don't buy into the soft-porn version of what women should look like.
If you are clean, groomed, presentable, then you're ok, I think.
ime once you start losing weight and it starts to notice, you will start to get your mojo back I am just getting to that stage now where i have lost a bit (lots to go) and am starting to take notice again
My DD is 9 and I've only just got round to losing the weight I put on when I had her . If you do need to change something you need to do it when you are ready and it feels right for you. Bringing up kids is hard enough without the added pressure of feeling you have to look like a supermodel every day.
I had a few years where I felt too busy and too tired to care much about my appearance, though I never looked awful. It is nice though, as I have done recently, to reconnect a bit with your old self and be trimmer and wear nice clothes again, I've also started doing my nails. My aim isn't to look the same as pre-babies, though, or even look much younger, just look nice for the age I am now. If it doesn't bother you, then there is no obligation, but as Angel says, it obviously does bother you a bit otherwise you wouldn't have posted about it.