Nether Portals not working right?

I've been playing a world and I was finally able to obtain obsidian and make a nether portal. I built the portal on a y of 64 and when I loaded into the nether I spawned near bedrock. This seemed unusual because I've never seen this happen before. I mined up about 3-6 blocks and found I was under the "lava sea." This means the nether was inaccessible, so I left and found that I hadn't spawned at the portal I built, but a different 3rd portal. This portal was about 130-160 blocks away from my original portal. No matter which portal I went through, the new or old one, I ended up in the same nether position where I was under the "lava sea." I decided to fix the problem by moving the portal, the same result happened, under the sea with a 3rd portal. Then I decided to destroy the 3rd portal and try again. This didn't work. Then I decided to raise the original portal and move it a couple of blocks away. I raised it to about a y of 75-80. This still didn't work. I don't know if this is really a bug, but I wanted to report it because I read that this is a recurring problem.