Sometimes i feel pregnant and others i dont?

Well, latley ive been getting lots of pregnancy symtoms.. Im always late by like a week on my period and when i do come on im only on for about 4-5 days.. When i hurt my stumoch or bump it im in agony for hours on end when normaly it dosent hurt, but sometimes iget lots of symtoms of pregnancy and other days i feel fine, i dont want to go out and spend money on a test if its not worth it.