Should I go to the E.R.??

I had to leave work early do to hurting. It started as a dull ache in my left side, I thought it was just period cramps at first. But it progressively got worse. I have to bend alot at work, and bending became and still is painful. The dull ache is still there, but gets worse when I bend/twist and it then radiates up to my shoulder blade. My back has started hurting some too. It's not getting much worse, it has moments when it worse but becomes tolerable again shortly. I don't have insurance so the E.R. is the only option I know. I'm trying to wait as long as possible before going, but if I'm not better my Sunday I'll have to go because I work Monday and I can't work like this. It had me in tears today.

It hurts to move around, which is why I had to leave work. It was bringing me to tears it hurts so bad to bend. And I can breath okay, but if I take deep breaths it hurts in my back/shoulder. Its exclusively the left side hurting. It's definitely more tha my period, I'm just not sure if I should waste the E.R.s time. But I need the DRs note for work if I'm still hurting Monday, and without insurance that's the only way to get one. I think it could possibly be my kidneys or a pulled muscle. Idk I've never felt anything like this.