Irregular vaginal bleeding?

I'm having irregular vaginal bleeding. I'm not on oral contraceptives and I'm sexual active. M last period was June 13 but I had unusual bleeding afew days before. Should I goto the ER to get some tests? I'm only 20 years old and thi has never happened before. The blood isn't bright red. And it isn't a lot if bleeding. I was on oral contraceptives a few months ago by I've had regular periods since I've stopped taking it .