So, what do contractions feel like?

No matter how much I read, I am unclear as to what I'm looking for.  What do contractions feel like?  Can they only last a few seconds at first? I'm 38+1 (whew!)  and this is my last week of work!  As of yesterday, cervix is soft, and zero dilation.  However, these pains I'm getting are radiating to my lower back and taking my breath away.  These pains have been happening since Thursday afternoon!