Welcome back, I hope you decide to stick around this time and manage to work through the difficulties you're having accepting your BDSM interest. We're here to help if we can!
Don't feel pressured to label yourself in this community. It might make you feel a bit more sure of yourself if you had a label, but it really isn't that important and doesn't affect what you enjoy in any way - you are you and you like what you like, regardless of whether you say you're a switch or not. Just go with your feelings and things will become clearer in time. Just had to get that out the way :-) Personally, I've written on my profile on here that I'm a sub, but I would definitely be interested in trying out the dominant role one day, with the right person, so yeah that's definitely a fantasy of mine. That right person will know me for who I am, and that's why I say it isn't important to label yourself because as an individual you are so much more than a label. Hope I'm making myself clear although I think I'm waffling...
As for freaking out about this site... hmm. Sometimes I wonder if by being here I'm putting too much emphasis on the role BDSM plays in my life, then I realise what does it matter? I enjoy reading the posts on these forums, enjoy replying sometimes, and find it helpful to start my own threads too. That's not a bad thing in any way, so what's there to freak out about? If anything being on this site shows that we're all pretty normal people and our common interest isn't so unusual after all ;-) Nothing to be scared of at all, and "wanting BDSM sex" can mean completely different things for different people so even if you read about certain kinks on here that don't match your own (and come on, that's bound to happen, we can't all be into everything) don't start thinking that those things have to become a part of your BDSM sex life - they really don't!
If you're not used to talking about this stuff and it makes you feel a little uncomfortable to discuss it, it's only normal for you to experience unusual sensations until you do get used to it, and can accept it as a normal "nothing to be afraid of" part of your life. That will come with time, if you give it a chance, and if you keep consulting the forums to see that there isn't anything abnormal going on here. Many things I've done for the first time have made my heart race, it's a completely normal feeling if you're not 100% comfortable here yet. As for being the beginning of subspace... well I guess only you can know that, but one question - does it matter if it is or not? You're still feeling the same either way, and I hope in time it becomes less scary for you. Remember you have support here on the forums in whatever ways we can help, and I hope we can!
Repeating what Snark said: relax and go with it - that means sticking around so I hope to see you post again soon :-)