So I've been trying to LD or even SP for a while now and I have had marginal success, enough to convince me I'm not a lost cause

My main problem however is that when I lie flat on my back [I'm told the best position for both LD and SP] and close my eyes I can't stop feeling my covers physically on me and my bed, I repeatedly try to lift a new set of arms from my body but always realise i can feel the sheets and I start itching uncontrollably completely breaking my concentration

I can never seem to get further than this, so how do you guys handle the transition between being able to feel your body, and then not, whats it like? whats my best bet for getting there?