Heya mate, UK doctor here. Hard to comment or give a clinical opinion online, but I would deffo reccomend seeing your local gp. Its nothing to be ashamed of. I've seen people's lives turn around with appropriate interventions, medication, counselling etc.
It sounds like you'd benefit from talking therapies at the least. The rules around counselling etc are different based on post codes, but generally the waiting times are currently quite long in the nhs presently, but your gp can sometimes refer you sooner depending where you are. Or in some places its an online self referral questionnaire, and the self reflection needed to refer is part of the therapy. If not I generally advise private counselling, beacon counselling is one I've refereed to if the waiting list is too long. These organisations try to discount rates.
If available, cognitive behavioural therapy may benefit you. It's a type of talking therapy less to do with talking things over or reflecting but on identifying changing unhealthy thought processes. It's quite helpful to sometimes talk these things over and begin the process of preventing putting yourself in a state of mind that could ruin your mood.
The relationship between anti depressants and weight is complicated. Some people gain weight because the meds essentially give them a boost in energy and whereas before they were eating nothing, with a normal diet they gain weight. I've seen patients maintain, gain and lose weight and I wouldn't let that put you off, generally the way these meds are titrated most patients I see have no side effects whatsoever (not garunteed but possible), and if one medication doesnt agree you can always try other meds till you find one that you tolerate.
TLDR: See your GP. You have a great deal to gain and nothing to lose. Best of luck mate, drop me a message if you need any advice in the future.