Did I just experience a seizure?

Hi, this is my first time on this site, but I'm concerned about what I just experienced. 

I have an undiagnosed condition which causes me to "black out" when I stand sometimes. Essentially, my vision fades to black, I get lightheaded, my heart races, and my blood pressure drops. I've been to quite a few doctors and had lots of blood work done, nobody knows why this happens. For the most part, if I'm in a familiar place, I can continue on like nothing is happening, or I'll just wait until it passes before I do anything (it usually lasts about 10-30 seconds). Every now and then I'll have a more intense "episode" and I'll have to rest for a few minutes before I can regain my bearings.

About 10 minutes ago though, I got out of bed to go to the bathroom and had one of these black out spells, but because I'm in my house and I can navigate without sight, I kept walking. However, when I made it to my door, the dizziness became unbearable and I put my hand against the door jamb to make sure I didn't fall. Then, things got weird. My consciousness got...blurry, to say the least. I was only about half aware of myself and what was happening, but I know that my body started jerking. My head and upper torso were thrashing back and forth, like there were waves rolling through it. I think I hit my head on the door jamb a couple times before I had the sense to lean away from it. That's why my consciousness went kaput. I honestly don't know how long this went on, it could've been 30 seconds, it could've been 5 minutes. When I came to, I was extremely disoriented and wobbly.

I've never experienced anything like this. My first thought was that it may have been a seizure, does anyone have any insight on it? Thanks so much for any advice or knowledge you can give.