Why not try to focus on the reasons why you want to lose weight to motivate yourself? You say that you are TTC at the moment and you fear that your weight may be causing a hindrance to the process.
In my case, it most certainly was. It took me 3 years of TTC and a particularly blunt doctor to give me the kick up the bum I needed to get myself motivated. Once I knew that it was NEVER going to happen unless I seriously lost some weight, I took it VERY seriously and didn't stop until I was a healthy enough weight for treatment to be effective - if you are having problems ovulating and they need to try you with Clomid, as I was, then you can only have 12 cycles of Clomid in an entire lifetime, and no more than 6 in a 12 month period.
I wasted 3 of them by being very overweight when I tried them. They then stopped me on it, and told me to go away and lose some weight. So I did, and three more cycles later I was pregnant. It isn't always that straight forward and I cant either diagnose if you are having any fertility problems or if that treatment would even help you personally BUT, if you get to the point where you need to seek help, wouldn't it be better to be in the best possible shape before you do, so that you can crack on with the treatments straight away, rather than having to wait?
I have no idea how old you are or how long you have been TTC for, but certainly, use that as your focus. It may be, that you lose the weight, it helps by itself and you dont need to seek further treatment, or you may still need some help BUT, you are in control of this - give yourself the best possible chance by taking charge of your eating habits NOW, getting your weight down, preparing your body so that any help that can be given, will be at it's most effective.
Good luck, I know how hard it is, but FOCUS, channel your motivation into the goals you want to achieve. You want to be a happy healthy parent - it's in your hands, just grab on and keep hold of it and give yourself the best possible chances. You deserve it.