Worried!!

Hi ladies I’m worried. I just need some advice. I just went to the restroom and when I wiped I saw this. I have been spotting a little bit of brown since yesterday morning. I had some back pain/ light cramping yesterday but it’s eased up. A little background this is my 4th pregnancy. I’ve only ever had light spotting/bleeding in previous pregnancies when I was checked or after sex. I had a Pap smear that day because I was a little behind schedule. I did have an ultrasound on Tuesday and they said that my Due date is probably off because they could only see the gestational sac. But not the baby. So I could be only about 5 or 6 weeks instead of 7 or 8. Got my positive results exactly 3 weeks ago. I’m just really scared. Has anyone ever had this happen to them? My doctor told me that if I have heavy bleeding and cramping to go to the hospital. But I’m so worried I want to go now.