I think others have fully covered some of the points you've brought up, like the vital importance of a safeword. AND YES, IT'S VITAL!!!!!
But I want to address the issue of pain and S/M within BDSM for a moment. I also wish to preface my comments with the fact that I am speaking out of my personal experiences only - everyone has their own individual views and pain tolerance levels.
I am not into S/M... yet I am definitely into BDSM. Believe me, I saw all the sub gals who were masochistic, and thought that was the i-ching of being a bottom at the local dungeon. After all, most of the pictures and videos we see of BDSM involves the bottom being restrained and spanked/caned/whipped/flogged/insert-pain-causing-action-here, right? But I found that I cannot tolerate pain play. It's not bringing the feel-good hormones, the release, etc. - it's just plain pain! So I started feeling like the horriblest sub girl around, the one who couldn't handle pain.
BUT... then I found there's sensual BDSM! It can be so intense and erotic and still put me in subspace. Sometimes it's soft, like a massage or a piece of rabbit fur being drug across my body. Other times it's stingy, as floggers are gently flogged onto my body. It can be thuddy, as someone uses various objects to hit me. It can be all kinds of different sensations.
Or rope! Yes, this is more bondage, but being tied up and having rope tugged and bounced while you're in it... different sensations!
And there's other things too: fire play, fire cupping, tens units, violet wand... and not one of those necessarily has to have you crying or biting your lip or screaming into a gag just because your pain tolerance may be lower than most.
My main point in all this is this: First and foremost, be safe. Safe, Sane, and Consentual. Take it easy when looking for Dom/mes or tops for play. Educate yourself! And realize that your kink journey needs to be what works for you. You won't care for everything at the buffet. But you need to fill your plate with what satiates you, safely.
I hope this helps.