Hi Tiko, yes, the headache will go - first 3 days are worst then miraculously you start to feel brilliant. Make sure you are drinking at least 2-3 litres of water.
To make a mousse you need the mix-a-mousse which you get from your CDC. You shouldn't have it for the first couple of weeks really but see it as something to look forward to. Once you have it you add a scoop to the shake powder and mix it in well before adding the water and blending it. I always use 300mls of water and blend for about 2 mins when making mousse and have always had good results.
Hope you soon feel better - don't try to over-exert yourself this first few days, reduce exercise etc and you'll soon be feeling good again - can't over-emphasise how the water helps
im the same as megan. i mix my shake powder and the mix a mousse together then add 250ml of water and blend for at least a minute then it goes in a bowl and in the fridge. i stir mine every few minutes which i find gives it a velvety texture but its definatly more angel delight than acctual mousse but i love it