I too started with a lot to lose. I've lost 87 and still have about 60 to go. It can be done, it takes committment and belief in ones self. I have to tell you though that I am so proud of myself and you will be as well. If you fall off plan, don't give up or chuck the day, just figure you fell once but it's OK and keep going. Forever I would blow an eating plan and then figure "what the heck I mells well eat now" I don't do that anymore, if I eat something I shouldn't, I get right back on plan. I've learned a lot about myself and I really like what I'm becoming.
Are you following the Spark Plan? Have you got an exercise plan?
Good luckand stay strong!