34 is by no means too old to find someone or to have babies. Try not to be down on yourself for the things that you cannot control. I think you are headed in the right direction by taking control of your weight issues. Losing weight by eating healthier and getting active will help you look and feel better, more desirable and perhaps help you come out of your break up blahs.
I'm in the same boat, as far as wanting to lose weight to make a better me...well, with the exception that my boat has a lot more weight to shed. Taking time to improve you is the best way to start. I know it's hard to stay positive when you are just coming out of a relationship, but things will get better. It will just take some time, and in the mean time you can start by making your body look and feel better and the mind will follow.
Good luck! Oh and when is your birthday?