I eventually went to sleep without SP
You go to sleep every night in SP, it stops you re-enacting your dreams

once I fall asleep in SP, will I automatically have a LD?
Nope. We are all in SP when we dream, we have an LD by realising we are dreaming. The technique of WILD is where you consciously enter the dream, you lay still enough to enter SP and proceed to transition into the dream. It's a tough technique so don't be annoyed about being 'too awake' to progress, it takes alot of practice for most people.
Check out some WILD guides if you want to LD that way, if not try looking into DILD which is where you realise you are dreaming, within the dream!
If you have any more questions, just ask!