Don't give up, 16!
I fought the same battle as you, losing and gaining the same weight, so many times. It IS disappointing, knowing how hard and long it took, just to slip back into the old ways of eating and lack of fitness. I bet I've gained and lost 50lbs, about 3 times..and this doesn't even begin to count all the smaller re-gains.
But, the good news is...I never gave up! Each time, I just prayed that *this time* would stick!
I'm happy to say, today, at the age of 50...I'm heading into my 3rd year of maintenance. Something just clicked in my head and all the past struggles, instantly, were gone. I'm 80lbs down and at the lowest weight of my entire life. So, see, it CAN be done! YOU can do this, too!! So don't give up the fight.