the same with me. very bad cramps and the neck is killing. i can soften these sides by adding pharma grade magnesium to my supps. you need more minerals while using clen.
clen is moving a lot of them out of the cells by sweating and heating them. simply you loose many minerals with clen. further clen rises your muscle tonus. also not good for well beeing.
look at the sympthomes for magnesium defiency. you will find things such as head ache, tremor, cramps and sleeping issues. now look at the sides of clen
so magnesium is important when administrating clen. so i recommend to start adding magnesium a few days before starting with clen. on the other hand... take magnesium a few days longer than the last clen.
dolph already said, for sleep issues... the last clen should be taken about 4 o clock. but this will only help a little bit cause of the half life of clen. i recommend in that purposes to take some sublingual melatonin 3mg. 30 mins before bedtime. that can help. i had noticed some benefits in the past. and last but not least... you really need to drink at least 1liter more than usual by working with clen. that will reduce headache, neck jaw and cramps aswell.