If mammograms been normal for past 2 years should I have one done this year? Also how often should I test? I’m 40.

Depends. answer depends on your risk factors for breast cancer and you family history
if low risk and no family history you can have mammogram every 2 years between age 40-50 and then annually.
Confusing guidelines. American Cancer Society recommends mammogram every year starting at age 45-54,then every two years.From 40 to 44 informrd decision making with your healthcare provider for women at everage risk.National Comprehensive Cancer Network recommends every year starting at age 40.And US Preventive Task Force informed decision making with your doctor 40to49.Every two years from50to75.Discuss with your MD.
See below. There is no black and white answer. You should discuss it with your doctor in light of your family history. You may consult this site for info:
https://www.uspreventiveservicestaskforce.org/Page/Document/UpdateSummaryFinal/breast-cancer-screening.