Help?

It's the weekend so I can't get ahold of my dr and I'm not sure if these symptoms warrant an ER visit or not. My husband and I had sex tonight. Afterwards I experienced a light brown discharge that still hasn't gone away. I also started spotting light pink/red about 3 hours after sex. My lower back hurts pretty badly (not in a cramping way but in more of a pulled muscle way if that makes sense) but it's been hurting for weeks so I'm not sure if that is related and I feel a bit of pressure and very light cramping/gassiness in my lower abdomen but I've also been dealing with the constipation that tends to come with pregnancy so it could just be that. Do I wait til Monday or go to the ER? I am 10 weeks today if that matters. I am freaking out. :(