I'm new to Burst

I created a burst wallet so i could have funds sent to it. I did all of the procedures carefully. I received 67391 BEX. wrote down my 12 words. When I went back in my wallet after, there was no more BEX. Nothing in it, no more assets??? i have noticed that my burst address upper left corner has changed??? i do have my 12 words written down? what happened exactly I don’t know. I’ve opened a btdex account in the meantime with the same 12 words. Is that the reason???