You came to the right place!! The most important thing is to be consistent, make yourself do it every day, even if it is just a little bit, because eventually it will become a habit to you. We have somewhat similar stats so I know how you feel, it is a long and hard journey but the payoff is so worth it in the long run.
One thing I tell myself about working out on those harder to stay motivated days is this: Workout for at least ten minutes, if after ten minutes, you want to give up then fine, at least you got some sweating in. But 9 times out of 10, I finish, and finish strong. Once you start there's no need to stop unless you are feeling sick or hurt!
OH and one more thing. This site has helped me tremendously in getting back on track. Utilize your tools, the support from people in the same boat is amazing here. Join up in some of the challenges to make it more fun, accountability threads are great too. Since you are in the 100lb club, there are specific threads for every ten pounds you are losing, such as one being in the 290s or 280s, I'm currently in the 230s to 220s thread, and so on. It's great to be able to communicate with others going through the same thing!