heart rate help!

hi! i used to run a decent amount in high school and early college but stopped for a few years and have recently started again! when comparing my heart rate and paces there is a hugeeeee difference. i used to run a mile at around a 7:20 pace and 150-165 heart rate, now I'm running a 9:30 mile and my heart rate is over 175 :( just wondering if this is normal because i took time off? and if there’s any advice on how to train back to my previous stats. my heart definitely does not feel great when running so i don’t want to overdo it but still want to get back to my original pace/HR! thank you!!