Unfortunately, hormone treatments work differently for everyone, and you never really know how you react until you get into them.
I've had endo since forever, diagnosed almost 30 years ago. I've done Lupron twice, and managed to get pregnant when I was 37, so Lupron does not necessarily affect fertility. A friend took it while undergoing fertility treatments and never managed to get pregnant. I don't think it was the Lupron that affected our outcomes.
IF you can take bcps, and there are so many out there that having issues with one means you will have issues with all, they are awesome for some women with endo. I was one of my doctor's first patients to simply take them non-stop: no periods. At that point, I'd done the then-available hormone treatments twice, but still ended up hospitalized when having a period. It was my only option other than hysterectomy at that point.
I took them for 9 years, then took 3 months off completely, then a year normally before my painful periods came back. Went back on non-stop for a few more years, then did surgery, Lupron (twice), and successfully got pregnant first try (assisted).
After a year, my periods were almost normal, but dr and I decided to go back on non-stop bcps because we didn't know how long that would be good for.
So... once I reached a 'certain' age, my dr and I decided to see if I could slide thru menopause gently. Not. After about 4 months, I had a period that woudln't end. Went on Aygestin to stop it, and it worked. I took Aygestin for the six months before my hysterectomy. Granted, at the time, I was already old enough that my estrogen levels were dropping. However, I nearly lost my job due to problems with my cognitive abilities. Post-surgery, I went on hrt and have re-acquainted myself with my brain.
Everyone's experience is different with hormones. At 19, you will hopefully have many opportunities to find out what your experience will be. Just remember, there are many different things to try. Your biggest challenge will be to find a doctor that you trust (and who trusts you) so that you will have a good partnership. I've had two doctors, and they were wonderful. I've also had a few that I've ended up walking out of.
Good luck. (Sorry for hijacking your post, OP!)
p.s. on Lupron, I had no hot flashes, but I was mean. And paranoid. I felt like I had no friends. And I didn't, because I was mean. But, after the 6-month course, I was myself again. No permanent changes. My friend had hot flashes. Her admin assistant quit when she heard that my friend was going on Lupron again.