Given your history of delayed cycles after using antibiotics, you can wait for a couple of days to see if you get a period. Normally, home pregnancy
tests can read well when performed 3-7 days after a missed period and with a fresh early morning sample of urine. You can either do a HPT or go for an estimation of the serum beta-hCG
titres if you fail to see your period in a week. The blood test
gives you a better prediction as it is sensitive and specific. If still in doubt, a trans-vaginal sonogram clears it all. Hope this helps.