if i have missed my period, shouldnt I be able to tell?

Hi,
Welcome to ehealthforum,
If you did not wait to have a period after removal of IUD, then you can get pregnant immediately in your cycle (if you have had ovulation). Chances of pregnancy cannot be ruled out as suggested by your symptoms (spotting, ‘feeling pregnant). Wait and watch for next periods at expected period date. Look out for development of any other new symptoms if pregnancy is suspected. Urine pregnancy tests usually start showing positive results late after about a week from missing periods. Sometimes they can also show you false negative results and hence cannot be relied upon for accuracy. Urine pregnancy test kits are calibrated ones, so they show positive results only after the hormonal levels in urine have reached a certain level. Blood/serum HCG level test are accurate and can detect pregnancy earlier than urine test.
Consider visiting your gynecologist/obstetrician at the earliest for examination (to confirm pregnancy related changes/signs in body) and blood/serum HCG level test (to confirm/rule out pregnancy accurately).
Take care.