Wow, what a transformation... I would be upset too. (and i'm a guy)
hopefully this advice will help.
First, the stretchmarks. During pregnancy you should have rubbed cocoa butter into your skin 2 times per day. However, it's not too late. Go to your local drug store and pick up some 100% cocoa butter. Again, rub it in 2-3 times per day while the stretch marks are still red. If they've turned brown (into bruises) then you will need to buy some vitamin e capsules... Take 1 per day with water. And use 1 and crack it open in your hand... It's 100% pure vitamin e, rub it into your skin (it's odorless, don't worry), and those stretch marks will be disappearing in a few weeks. (yes, literally.. Weeks.)
second, the weight is something you need to start working on immediately while your hormones are still stabalizing, otherwise it'll be an uphill struggle for a long time to come. This is your metabolism that needs changing... And to be honest, to get back to your former body-size you don't need to join a gym---however, to get the firmness back, you will need the gym. To save my breath, read the outlined directions in this post here:
http://ehealthforum.Com/health/topic30833.
Html it will be enough to get you started.
In you case, you will need to increase your metabolism now, while it is still very flexible. This means, you need to get active. Moderate cardio twice a day, small meals throughout the day, and stay away from complex carbohydrates. Now listen, it sounds tough.. But if you don't start now, it'll be a lot tougher. Get yourself together, and in a year once your metabolism stabalizes back to where it was you can enjoy all the chocolate cake you want, and laze around all you want... But right now, you need to buck up and get back on track.
If you need more specific advice, don't be afraid to ask or pm.
Good luck,
justin