A lot of what you’re describing are puberty/hormone dependent symptoms, is it possible that your body is just playing catch up now that it has the nutrients to actually do what it needs to do? I was also extremely short and malnourished growing up and I was diagnosed with celiac in 2019 and months after going gluten free I started getting heavier, longer lasting, and more frequent periods (pre-diagnosis I was lucky to get even 4 a year, post I was getting them roughly every 40 days). Getting on birth control entirely regulated my cycle, reduced the bleeding, almost completely eliminated the pain, stopped me from fainting during my period, reduced the acne breakouts the days leading up to my period, etc. Unfortunately, I can’t speak on the mood swings and low energy as much even though I experience them as well because for me, they’re obviously explained by my depression. You’re right that you are more susceptible to other medical issues, but it may be worth to attempt to exhaust the more common “this is hormonal” or “this is stress induced” solutions first. You know your pain and your body best though, use your best judgement.