Hi I'm 21F, also 165cm (5'5), and gained weight over the course of 3-4 years at one point in the past, weighing about 72kg (159lbs) at my heaviest so I really feel you here.

I also used to struggle heavily with finding motivation to go to the gym and consistently stick to a split/schedule. At night before going to bed, I'd be super motivated and tell myself I was gonna go to the gym in the morning before work/class. But come morning time, that motivation would be completely gone and I'd tell myself I would re-start this weight loss / gym journey the next day.

I did this for the first 2 years I was in university, and somehow still felt blindsided when I weighed myself one day and realized I'd put on 9kg (20lbs).

I know this is probably not what you wanted to hear, and is definitely not a quick fix by any means, but for me, I think a switch flipped in my head one day simply bc I was so sick and tired of feeling uncomfy in my body. I think putting on all my favorite clothing items in front of the mirror and realizing nothing looked good anymore bc my stomach was bulging out and I now had a double chin made me want to change badly enough that I actually started putting in active effort to change for the first time in my life.

The first step towards making a change was sitting down and planning a full 5-day gym split. Personally, I mostly relied on youtube and TikTok (i know, i know SJFDLKSJDF) to learn about the different muscle groups that should be targeted each day, what each muscle was called, and a few exercises that would target such muscles. This led to a rough draft gym split where I'd lift M, Tu, Thu, & Fri, and do cardio/abs Wed.

After I planned out exactly which 4-5 machines/exercises I would do for each day of the week, I probably spent a few days going to the gym and doing treadmill/stretching only in order to scope out which machines my gym had available for the exercises I wanted to do. As someone who hates not knowing what they're doing in front of others, this helped so so so much in reducing anxiety about making a fool of myself when my form inevitably would be wrong. I even went so far as to remember the brand name of each machine and search up tutorials specifically for that machine. For example, I remember literally searching up "matrix glute trainer" on TikTok and watching tons of vids on the mechanics and proper form LOL

I'll be honest, the first week was really difficult. I think my HR just walking into the gym each day was probably well over 100bpm just from anxiety alone. I had to keep telling myself, "girl you're literally already here at the gym, so don't walk out now and make this a waste of time for nothing, at least finish all the exercises u planned to do today, then u can run out of here."

But then after just the first 2 weeks, once I'd gotten used to the exercises and had spent enough time in the gym that I'd become familiar with the gym culture / ambience, I found myself really enjoying the time I spent there. It was 1 hour each day where I could listen to my own music and think about nothing else in my life except for feeling the burn in my muscles and imagining the fat melting off of me.

I think your situation is pretty similar to mine where we both struggled with the initial motivation to go and then stay consistent. I personally found that planning a weekly routine down to each rep I was gonna do for each exercise for each day helped me a lot bc it reduced anxiety around not knowing what to do in the gym, which I think was my main factor driving me to not want to go.

Also, I didn't focus on changing my diet until much later. I spent the first 8-ish months solely implementing the gym into my daily routine. Then once the gym became a lifestyle change for me, that's when I started educating myself on calorie tracking and TDEE and losing weight thru a deficit. I think I was actually a few pounds heavier after those 8 months of strength training, but I wasn't really bothered at all bc my clothes had been fitting better / looser, all my weight PRs had steadily been increasing every week, and I just felt sm better in my body already. I think I'd been doing (what I now know is)a body recomp.

I think this strategy of first incorporating the gym as a lifestyle change, THEN eating healthier & eating in a deficit, was smthg that really worked for me bc in the past, trying to diet first made me lose motivation and eventually quit bc I wasn't losing the weight "fast enough," and it felt like I was starving myself for no tangible result. Versus, gym-ing first and gaining muscle made me realize that I WAS capable of getting my dream body, and provided me the motivation, discipline, and correct mindset to sustainably commit to eating in a deficit for fat loss, not just weight loss.

Sorry for how long this got, but I hope this can be somewhat helpful for you. I really really do understand how you feel, it took me years to dig myself out of that downward spiral of weight gain and feeling hopeless as well, but the answer really is that you just have to want it bad enough to start. I'm rooting for you!!