OK you are looking at 23-24 weeks. Maximum safe continuous weight loss is normally recommended at 2 pounds a week, so this is possible if you are sensible.
The difficult bit first. Try not to be too focussed on the scales, they are one of the least accurate measure of fat loss available, and will often leave you despondant when there is a slight increase. Take weight measurements weekly or daily, but just for trend analysis not constant progress measure. Try using clothing fit and general appearance as a guide, not easy but often more accurate.
Why are scales inaccurate?
Fat is 3,500 calories a pound and water levels in our bodies fluctuate immensely. People will lose 2 pounds in a day and be impressed put it back the next and not see the point. 2 pounds of fat loss involves using 7,000 calories more than you have consumed, unlikely in one day. If you dehydrate one day the body will hold onto it the next if it can, so that 2 days could contain constant fat loss, but you wouldn't know.
You will gain muscle which is 75% water and therefore immensely heavier than fat. This will burn energy all of the time so muscle is your friend and the scales will disagree.
You have come to this looking long term. Keep this in mind and avoid sudden quick fixes, which often reverse as soon as you stop. There are exceptions, but they are the minority.
Diet wise I always ask people to fit the balance into the food pyramid, google will show it, and increase or decrease amounts of everything in balance. This means you will stay healthy, be able to keep the diet up for as long as you need and not have to wonder what to eat at the end, because it's just a matter of the same but a little more of it to maintain if you were losing.
Exercise wise you will want things you can do without damaging yourself. I don't know the details of your birth, but if it was ceasarian or there were complications these will have to be taken into account when considering your regime. I don't need to know details, just think about what has happened and if something looks of feels wrong don't do it.
P90x is something to do when you are reasonably fit already. Failure to remember this will result in immense pain and possible injury. There is nothing wrong with this system, but I would say have this as your final 90 days and spend the first 73 building up to a level where you can do this.
The principals behind P90x could be utilised for your training now and you can do a more basic version leading up to it. The core idea is to use MSE circuits, cardio and mobility in combination to get muscle tone and weight loss, a good system and something I used to teach before it was given a nice little name.
Treadmill can provide good fat burning aerobic work. Start with spead walking, making sure you don't break into a jog or run for at least a couple of weeks, you are heavier than you are used to and the impact of this could be an issue. Speed should be set to as high as you can while breathing freely, to test breathing talk aloud, if this is hard slow down. The longer you can be doing this for the better but don't try doing everything at once. Spending 3 hours on the treadmill and 4 days recovering will not help, while 2 lots of 20 minutes a day everyday would be incredible, half this would be a very good start.
Circuits
Find some in your DVD collection and do them 3 times a week if you can, twice if not. You want a balanced workout that uses the whole body with limited rest between exercises. Start easy, and build up. I expect Zumba will have some suitable workouts, though don't truly know. Make sure cool down and stretch are part of the program. If there is no warm up do this after a walk.
The same will be true for yoga or pilates. These to be done on other days and again starting very easy. Ideally this would follow a walk so you are doing mobility warmed up. Again 2 or 3 times a week.
Remember that you are after overload not injury. You should know you have trained the day after but not be in agony. If you are learn and wind it back next time, don't quit.
Most important, find stuff you enjoy. If you try circuits on one DVD and hate it do Zumba instead and vice versa.
