Weight gain please help.

So I've struggled with eating disorders in the past I was 210 then 160 then 230 to 120 and now I'm 172 and I was 162-165 last week!..Im so depressed and I eat junk food all day but I can't stop it's like if I don't have it It seems like I'm more depressed like the serotonin doesn't spike unless I have sweets and salty foods..Ive been vegetarian for 2 weeks(Mainly for animals but heard it also helps with weight loss)and I've been drinking a gallon of water for 3 days now and It seems the number is still growing on the scale..I weighed in at 172 today and I was 171.8 yesterday...So far it's been a pound everyday..I'm so scared to be obese again.I hates myself to the core and said id never be that way again..I look in the mirror and gasp at how big I look..My clothes even feel tighter..I'm so ashamed and I don't know what to do.