Dizziness and rapid heartbeat

I’m a 20 years old female student. I consume allerpid tablets on a daily basis. Before that, i took, if I’m not mistaken 5mg loratadine tablets. But as days go by, it doesn’t seem to work. Later a pharmacist gave me allerpid tablets to try and it work. Now i cant go a day without consuming it because if not I can’t focus on anything; in class and especially driving without hurting my abdomen. Two months ago a pharmacist also told me to try consuming blackmores vitamin c. I’m not sure if it helps because i don’t see any changes. It’s only recently that i noticed my heart often beats very fast and whenever i get up after sitting and lying down, i often get dizzy as if I’m about to faint. It’s all blacked out. Should i stop taking the meds? If so, what should i do to make the sneezing, watery eyes etc stop? Thank you for your time