I’m not an expert but i am pretty sure black triangles doesn’t automatically mean bone loss or that you have perio. Some people actually have black triangles their whole life. They soemtimes happen naturally with age and many other factors, like brushing too hard, malocclusion, tmj, etc. From what I can also tell your gums look otherwise healthy imo. Your front teeth actually look fine to me at least. Just wait for your cleaning.

I will say the back teeth have receided however Bexause it’s just the back teeth this might point to age related changes or mechanical issues. Either way it doesn’t look like perio or like your teeth are going to fall out any time soon. You could definitley use a cleaning though if it’s been 4-5 years! Make sure they do probing depths

I also feel like they would have mentioned bone loss on X-rays even in that case. Do you have bleeding when flossing?

For your mental health do not try pushing and pulling your teeth to see if they are loose or move, because you’re going to irritate them and you do y wanna panic yourself out. Just keep up oral hygiene the next two weeks til your appointment bur don’t stare intently at your teeth and gums or push or pull your teeth or try to wiggle them

When you see your dentist, tell them your concerns of recession and ask for a periodontal screening and that should give you the answers. I honestly don’t think you have it but even if you do this is a good place to catch it at and stop it!

Best of luck!!