Very Worried - 5 weeks today.

I am 5 weeks today, started spotting two days ago, has been light pink/brown on and off since then. Had a US yesterday and they were not able to see anything at all. Sent me back for more blood tests to see if the levels are rising, had some instead cramping yesterday with constipation - had a lot of gas and felt better when it came out so thought that might be related, but spotting this morning is still pink and light, my boobs don’t seems as heavy and sore and not feeling nauseas today. I’m so worried about what is happening.