One meal a day is fine, lots here do it’s not me though I’m like my food too much lol. Do you count your macros for the meal you eat? e.g.) carbs, protein, fat etc. it’s very important to know that you are getting enough nutrients from your meal also if your carbs are still low enough to not affect your blood sugar. Even in one meal if your carbs are higher than you can cope with it’s going to push your numbers up. I see in another post you are getting a meter so that’s good, test right before you eat and then 2hrs after, I would also personally test at 3hrs too for a while until you are happy your blood sugars are under control.
I lost over 11st and still losing, but it took me a lot, lot, lot longer than you, I did low carb then keto 1200 calories a day I am very curious in how you are doing it, if I’m honest I think if it was me that would be my biggest concern right now and would be pushing my GP to find out why
edited to add: meant to say you can use a site such as MyFitnessPal to track everything you eat, you can put in your own meals or use the database, just make sure that the carb count for things are net and not gross. I use the free part of it and find it sufficient to track all my macros, calories and weight loss. You can pay for a premium membership but I don’t think it’s worth it. There are other sites but I’ve never used them, maybe others members have and they can advise on those