Yes you can call the ER for advice and they can let you know whether or not you should come into the ER for treatment.
Sometimes things can be less serious than they seem and sometimes they may be serious enough to warrant an ER visit.
If it's not a real emergency then you can call the ER to see if they think you should come into the ER for treatment and they can give you some advice.
But if you do think you really do need to go to the ER then go ahead and go so that you can get there in time.
If it's a life and death situation such as you having a heart attack are bleeding heavily etc then call 911 and get an ambulance on the way for treatment.