I came here to post something similar.
I feel the same way.
I did *try* to get a start on my weightloss at a few weeks PP, but it became too much.
And now I'm eating like crap and not exercising too.
I'm going to give you the advice that I do not want to follow for myself.
Even though its been 12 weeks, that is not long after having a baby. I've had3 and I can tell you that regardless of how the baby sleeps, eats, is and everything else, babies require a lot fo care physically and emotionally. I don't remember if this is your first (I'm thinking no, I know we talked on this board while we were pregnant)
But all moms whether is their first or not, have that initial loss of self and "me time" even if you already have kids, as they get older they demand slightly less of your "self" time, like you can shower, sleep, sit down for a minute. Babies..not so much. Plus with BFing, as nice as it is, its still demanding a part of you for every feeding. Even if you pump for a bottle, you still ahve to take that time to pump.
Granted some mothers may not feel that full loss of self which each baby, depending if they have a lot of support (i.e. someone to watch the new baby often so they can shower, get out alone)...
Now for the weightloss.. Yes eating healthy feels good, yes exercise feels good, but lets face it, if it came to us THAT easy, no one would be fat. It does require some effort. The pay off is nice, but its also delayed.
I know when I've spend the day with a cranky baby and my other 2 kids, I find stress relief in eating. And high carb high sugar foods give that insant pay off. Like a cigarette or wine, only I chosse not to drink or smoke, food is my drug of choice.
I do like exercising. I really do. I love to get up early (assuming I wasnt up all night with a baby) and exercise, assuming I dont have a baby to care for first thing in the morning, but this is not the current situation.
So if I di get some down time when the baby naps, I really want to sit and do nothing, some time to myself...but what I really end up doing is cleaning.
It does get easier. They get to an age where they can go in the walker, sit in the high chair with a snack, or in the stroller for longer periods with a drink or toy. But these early months, there's not alot of down time, and when it happens, who really wants t exercise? A luck few. Not me.
Also with the eating, I think the older the baby get and the less meal time is a rushed and stressful time (eating with one hand while nursing baby, at practically every meal) then the less you will just fall back on crappy eating. I know that's how it is for me.
Anyway, I know that feeling because despite my advice I feel like I failed too. I have given up lsonig weight and decided today to come back SLOWLY. I'm not going to put a lot fo pressure on myself. And I dont think you should either.
The babies will get older, and there will be a time when diet and exercise are not so stressful. And you will have more energy to focus on your weight. Until then baby steps. Dont let weightloss add anymore stress or consume anymore time than you can handle right now.