I feel your pain. I have been in a constant lose 10, gain 15, lose 15, gain 10 cycle for years now....yesterday was the first time I weighed in under 250 lbs (scale was 249!) in over 3 years.
You can do it. Take it one day at a time. Come here to vent/scream/gloat/get support - what ever you need.
You may find it really helpful to journal also - not just what you eat but your moods/feelings/worries that are on your mind that day. One day, being able to look back and see how far you have come will make you feel wonderful.