Your stomach muscles are probably just sore from all the hiccuping you have been doing.
I know it's impossible that's why I'm asking I had the hiccups for two days in a row the doctor said from the impact of the hiccups which uses your stomach muscles it just upset the baby and made it move a Lil bit....it was asking for other people's opinion or to see if anyone has had this happen to them
Your umbilical cord? You mean your baby is tugging their umbilical cord and you think your feeling it? At 8 weeks That's pretty impossible especially to the point you can feel it. Pretty sure you won't ever feel them tugging it. Your probably experiencing round ligament pain which is the stretching of your stomach muscles.