As mentioned, it takes ~6 weeks to see the effect of taking the synthroid on your thyroid hormone levels. And even then your hormone levels can fluctuate, so they’ll retest periodically until you’re at the target levels.
I got diagnosed with hypothyroidism about 5 years ago. I’d probably had it, undiagnosed, for ~20 years if I go back to when I suddenly gained a lot of weight. My other symptoms - low blood pressure, really low heart rate, fatigue - had been around forever, just gradually worse. I started at 25 mcg, then 50 mcg, finally at 88 mcg. And that process took about a year and a half. It was about another year at my current dose until I started noticing any effect on my symptoms.
So I think your doctor’s estimation of “several months” is probably on the lower side.
I need to eat a lot less than everyone else I know. And it took a long time to get used to that, plagued by cravings the entire time. It sucks, but so it goes.
When I was hyperthyroid I felt TERRIBLE. Constant sweating (and associated skin rashes/acne), palpitations, tremor, insomnia, dramatic heat intolerance, general weakness and fatigue.
You do lose weight but you feel ridiculously horrible and you are doing a lot of damage to your body, losing muscle mass, thinning hair, etc. And then you gain the weight back quickly when you get your levels back in order.
As a woman with hypothyroidism and a handful of other metabolic disorders too, who was told by her parents that she was fat long before she was actually fat, who makes all the FitBit meters turn green every day, eats in her weight-loss calorie range, and is still lucky to lose a pound a month … suck it up, bucko. You can’t double up on your thyroid meds.
I struggle with appetite when I’m not watching carbs. Maybe try that.
I feel for you. It sucks to be overweight. The first time I dipped my toe into the obese end of the pool, I started sticking my fingers down my throat to puke up my food and reduce calorie intake. It was stupid, but it was still safer than what you’re doing.
There are options available to overweight and obese people to facilitate weight loss. None of them are easy, or fun, and a lot of them involve learning to be hungry for long periods of time. Many involve surgery. All are a better idea than double dosing your synthroid. Ask your doctor about them, see what people are doing online, check out your gym. Make it a project. Try a little of everything and see what works for you. Good luck!