Im so confused.. plz help? ami actually pregnant or not?

Hi guys ive been ttc for 18 months now after i had my last m/c. since my m/c my periods have been crazy n come when they decide.. anyway basically my periods for quite a few months have been coming every 6ish weeks. but my last period came after 3 weeks. anyway that was 2 n a half weeks ago.. today i did a pregnancy dip stick test and it showed a faint positive, so i did another 2 and the same! i went to buy a clear blue digital and it said pregnant 1-2 weeks. i couldn believe it so i did the other awhile after but it said not pregnant. im so gutted as i dont know what to think now, could i really be pregnant? or was i just wishful thinking?? ive been trying so long to get pregnant again i feel like i dont know what to think. has anyone had this situation before? was the outcome good or bad? thanx in advance.