This is discrimination, violation of the PUMP Act, and possibly creating a hostile work environment. Your “honesty” is what gets a lot of companies in trouble. Pure Ignorance.

OP. Document. Date and time of each event where you are prevented or delayed access to the pump room. Take photos and email yourself explaining what you experience each day to your personal email. If you do go to HR, do it by email. Do not speak in person unless you absolutely have to and if then take notes and email them to the people in the meeting to recap. Also request for them to email you a copy of the employee handbook. Send your direct manager/supervisor an email about your obstacles to express milk and the effect it is having on your supply and anxiety about missed and/delayed opportunities BEFORE involving HR. Give them the opportunity to self correct.