I’m a 5’9” guy and I don’t do IF anymore, but I did lose around 60lbs with IF in my early 30s. I also have a lot of the same quirks you do: I easily gain weight that at the very least looks like muscle; even when I was at my heaviest people were very surprised at my weight; I have a lot of unavoidable/chronic stress; and I have a history of mental illness. I also have a history of injuries from exercise or sports.
I find for myself that the stress component is a huge part of successful weight loss/maintenance. It changes my sleep quality, makes me retain water, seems to slow down my metabolism, increases the severity and frequency of hunger pangs, etc. Stress impedes not only weight loss but physical strength and muscular development/recovery as well. If I’m handling my stress, I have zero issues maintaining the discipline I need to continue my regular diet and exercise routines to the letter, even with lots of distractions.
Anecdotally, things that have worked for me include making sure I get good sleep, making sure I’m social (I’m an extrovert), increasing my low-impact cardio on top of my regular lifting/running schedule, going low-carb (not keto) during the week, making sure I get enough protein, and making sure I have absolutely mind-boggling cheat days weekly. Like entire stockpots of healthy food with a moderate amount of carbs, enough for 8 meals in one day.
Also what worked for me (and obviously your mileage may vary) was leaning into the muscle development. During parts of my IF experience I was lifting weights 90 minutes 6 days a week, but I also focused a lot on getting incidental exercise, like walking in circles when I talked on the phone. When I’m stressed I tend to get less of that incidental exercise so even if I’m lifting heavy and running, those workouts are like 95% of all the physical activity I’ll do over a day and that’s just not enough.
You’re threading a needle right now: the factors are your calories out, your calories in, and the stress you’re under from exercise, weight loss, upcoming events, managing your diet, your past, etc. Changing any of the factors is going to change the others, and you kind of have to just keep wiggling until you find something that works for a bit. I’d start with walks, sleep, or nutrition and go from there - but take it easy. Being more “strict” or “vigilant” right now is going to increase your stress.
Fast 6 days, cheat one day. Or even fast two weeks, cheat one day. Make sure you’re eating at least 1200 calories of good, nutrient rich food. Also, give yourself grace and patience. IF is no easy task and being hard or down on yourself makes it much worse. Good luck!!
Not to say you need to track compulsively, but I find that tracking what I’m actually eating for a week helps me to see what’s going on. That and prioritizing my sleep. Stress and lack of sleep can really affect our bodies, and it’s amazing how many calories can be fit into an 8-10 hour window.
With the wedding coming up (congratulations!), I would suggest being gentle with yourself for the moment and focus on sleep, stress reduction, and making sure you’re eating healthy, without any junk carbs mixed in. Maybe try to extend time between meals within your eating window (getting rid of snacks). Nothing too drastic, you have a lot on your plate right now. Once you’re back from your honeymoon is plenty of time to get strict.