Should I go to L&D?

My doctors nurses line is closed for the weekend, not sure why, so I'm asking here. I've been having some pretty painful menstrual like cramping. It's constant; not going away even with drinking water and resting. I've had a few BH contractions, but nothing regular or terrible, but the cramping is so painful I'm almost in tears. I also have pretty bad lower back pain. I'm debating on taking Tylenol, but was wondering if this was a sign of labor? I'm only 35 weeks, so I don't want to risk anything. I never went into labor naturally with my first, I was induced at 39 weeks, so I'm not sure when to be concerned and what's normal. Should I go to the ER to get checked, or should I take Tylenol and see if that helps first?