What Causes Stomach Cramps And Tiredness After An Early Miscarriage?

Am 29 yrs,weight is 57kg,height 5ft,5 inch.I was 5 weeks pG On 18th/ 04/2011,i had light bright red bleeding n painful cramps that same day n spotting in d nxt 2 days,then on the 27th/04/2011 l had severe cramps and bleeding for 5 days,l went for US n was told am no more PG,a week n 2 days after bleeding stoped,l had sex n l notice l had lots of slipery mucous b4 unprotectd sex.2day is 13th/05/2011,l'v bn having cramps n abdominal discomfort on n off n feeling neauseated,iritating stomach,tirednes,eating n drinking water alot.l dnt no wot is happenin.is it normal in abt 2-3 weeks after an early miscarriage.