Sent to HR for pumping

My boss just told me I have to go to HR because pumping is now a problem. My supply has gone down from 6oz to 2.5/3oz so I need to take a little more time to pump to hopefully get my supply back up and I told them that I’ve having trouble. HR told me my first day back I can have my 2 15 minute breaks and my lunch then pump after my 2 15s. I’ve been doing that and now it’s a huge problem. I don’t know what to do. This is a dead end job and I’ve contemplating leaving so many times so this is making it worse. What are my rights in the US?

I have not gone to HR yet because I am upset and I am afraid I will become emotional. :( so I am posting on here and cooling off before I go. Thank you so much