How can I change my lifestyle?

Start with the easy things. Small changes, compounded over time, can really add up.

you just need will power

Guess it depends on how you want it to change.
You can start smoking or stop smoking, you know?

Well I think it starts by setting your intention.

Figure out how you want your lifestyle to end up, and then make each step you take something that furthers that goal.

That's a pretty big change

Maybe you could start by covering up your boobs a bit better.