Sounds like a WILD to me. This is how I typically enter a LD - just without the screaming part
Lying very relaxed and then start moving my dreambody by either just sliding or falling, or by a rocking motion that grows until moving freely. The screaming part sounds a bit like what can happen during a false awakening.
With a bit of practice one can easily have a chain of WILDs that way. For me often the LDs get more stable later in the chain, so I can then have a longer LD. I am now starting to be able to sometimes jump back to where I left the previous LD, but most times I have to start again from my dream bed.

Now that you know how it feels, you can do it again!