hmmm....well technically your problem has nothing to do with autosuggestion, becuase with autosuggestion you only need to suggest it to yourself, once or three times and thats it.

if your mind is going on fire about lucid dreaming and wont shut up *therefore ruining your sleep* why not try some relaxation methods? I find that when I count to 100 even some where in between random dream like thoughts invade my head, making it even difficult to remember what number comes next. im not sure how counting would work for you, but there are other relaxation methods.

empty your mind and lie still, two things will happen. random thoughts will come back and you will once again fall asleep naturally. or, you will get HI and can attempt a WILD. either way, im sure relaxation methods can help you! the tutorial here is a good place to start

and I know your pain, I've been suffering from insomnia lately and it really really sucks since I do want to dream and be lucid!